Which Virus Has the Highest Death Rate?The Virus Risk Perspective — 15 viruses, each figure with its denominator

How does a measles exposure compare to a dengue infection, or a hantavirus case to seasonal flu? This tool lines up 15 viruses on the same funnel — exposure, severe outcome, hospitalization, and death — using figures reported directly by CDC, WHO, and NIH.

Last reviewed: September 2026 · By Andy Wilcox, independent researcher

The Short Answer, and Why the List Below It Is Harder

Rabies — effectively 100% once symptoms appear. That one is not in dispute and needs no caveat. Everything under it does, because the figures are not counted on the same basis, and most "deadliest viruses" rankings you will find do not say so.

The 10 of 15 viruses tracked here that have a published US case-fatality rate, highest first, each with the denominator it is calculated on. The other 5 are listed below the table. Figures and sources are the same records that drive the full comparison below — see each virus's detail card for its "data as of" date and primary source. The denominator column is the point: a rate "of people who develop respiratory symptoms" and a rate "of all symptomatic illnesses" are not comparable numbers, however similar they look in a list.
VirusCase fatality rateCounted as a share of…
Rabies (US) 100% Of clinical rabies cases — virtually 100% fatal once symptoms appear (not the 1.4M annual exposure evaluations).
Hantavirus (hantavirus pulmonary syndrome, US) 38% Of people who develop respiratory symptoms (CDC's About Hantavirus page). CDC's surveillance page separately reports 35% across all 890 laboratory-confirmed hantavirus disease cases 1993–2023, including 31 non-pulmonary infections; the 38% is kept here because it describes clinical HPS, the syndrome this record is about.
Powassan virus 13.2% Of reported US cases, 2004–2025 (CDC's own deaths-by-year series). 2024 alone: 9 of 60 (15.0%); 2025 preliminary: 10 of 76. Replaces the 11% figure (a CDC 2006–2016 cohort, 11 of 99 cases), kept as the earlier history point. Reported cases are predominantly severe neuroinvasive disease, so this overstates the fatality of infection overall.
West Nile virus 9.6% Of reported WNV cases (173 of 1,808 died; 91% of cases were neuroinvasive). Among neuroinvasive cases specifically the CFR is ~13%. Most WNV infections are mild or asymptomatic and never reported.
Avian influenza A(H5N1) 1.43% Of reported US H5N1 cases in the 2024–25 outbreak; most were mild farm-worker infections. Re-verified 2026-09-15 against CDC's current situation summary (March 6, 2026): no further H5N1 cases or deaths since the March 2025 inputs. CDC's page now counts all A(H5) subtypes — 71 cases and 2 deaths — because the 71st case (Washington, November 2025, fatal) was an A(H5N5) infection (WHO DON 590), which sits outside this H5N1 record.
COVID-19 (SARS-CoV-2) 0.2-0.51% Of symptomatic illnesses (2024–25 modeled season); varies widely by variant, age, and vaccination.
Dengue 0.2% 2024 figure, of reported US dengue cases (97% travel-associated in 2024). CDC's ArboNET data page publishes case counts only; no 2025 death count or fatality proportion had been published when the source was re-read on 2026-09-15.
Measles 0.13% Of reported US measles cases (2025: 3 deaths per 2,289 cases).
Seasonal influenza 0.09% Of symptomatic illnesses (CDC modeled burden).
Mpox (monkeypox) 0.04% Of reported US cases in 2025 — one death among 2,519 cases, as stated by CDC (2024: 0.18%, five deaths among 2,803). Deaths are those confirmed by the jurisdiction as attributed to MPXV. No US clade Ib deaths have been reported. The 2022–23 outbreak figure this replaces was 0.13% (clade IIb; ~94% of deaths in severely immunocompromised people).

The 5 missing from that list matter more than the 10 in it

Ebola virus disease, Norovirus, Respiratory syncytial virus (RSV), Zika virus and Marburg virus disease carry no case-fatality figure here at all. That is not an oversight. A published US rate on a basis comparable to the others does not exist for them — for Ebola and Marburg because the United States has had too few cases to compute one, and for the others because death is not the outcome the surveillance measures. Rankings that place Ebola and Marburg at the top are quoting outbreak fatality rates from African epidemics, against a denominator of laboratory-confirmed cases in settings with limited critical care. That is a real and terrible number. It is not the same measurement as the ones above it, and putting them in one ordered list implies a precision that does not exist.

The single comparison worth internalising: hantavirus at 38% is a share of people who already have respiratory symptoms. COVID-19 at 0.2–0.51% is a share of all symptomatic illnesses, a vastly larger base. The gap between them is genuine — hantavirus is far more lethal to the people it makes ill — but it is not the 100-fold gap the two numbers appear to show, because the two denominators are counting different populations. Every figure above carries its basis for exactly this reason.

What follows is the full comparison: exposure, hospitalization and death for all 15, each linked to its primary CDC, WHO or NIH source.

How to Read This Comparison

Every virus below is measured against the same four-stage funnel: how many people are exposed or infected annually, what share progress to a severe outcome, what share require hospitalization, and what the case-fatality picture looks like. Where a public health agency has not published a figure — or only publishes it as a range — this tool says so explicitly rather than estimating a number no agency has confirmed. A "Data not available" label means exactly that: not zero, not average, simply unpublished.

Every figure links back to its CDC, WHO, or NIH source and carries a "data as of" date. Diseases with an active or rapidly changing situation — currently Ebola, measles, mpox, West Nile virus, and avian influenza A(H5N1) — carry a visible "Evolving situation" flag, since their figures can shift within weeks.

Case counts, hospitalization figures, and mortality data on this page are sourced directly from CDC, WHO, and other primary public health agencies as cited inline. This is statistical and educational information, not medical advice or a risk assessment for any individual. Figures for ongoing outbreaks change frequently — check the "data as of" date and linked source for the latest numbers.

Figures are shown for the United States and, where a comparable annual figure is published, for the world (WHO). Use the Geography control on the chart and table to switch between them; each virus's detail card shows both side by side. Global figures that aren't a like-for-like match to the US annual number — a children-only estimate, a multi-year outbreak total — are marked "Data not available" with the actual figure kept in the source note, rather than charted as a misleading comparison.

New to some of these viruses? The plain-language virus glossary gives a one-line explainer of each, and every virus also carries a short definition on its detail card below.

For the practical counterpart to these figures — which disinfectants actually inactivate each virus, and how long each survives in the environment — see what kills viruses: a disinfectant guide by virus type.

For the economic counterpart — what one case of each virus costs a hospital, society and the economy, with every division shown — see cost per case, virus by virus.

Four pairs people actually search for are set side by side with their denominators explained, reading from these same records: COVID-19 vs seasonal flu · Ebola vs Marburg · hantavirus vs COVID-19 (presentation) · H5N1 vs seasonal flu. Only pairs with demand evidence are built; the table below already compares all fifteen.

Severe outcome rate is the share of infections that progress to severe disease — ICU-level illness, respiratory failure, or another organ-threatening complication — as defined by the citing agency for each specific virus.

A note on case-fatality rates: the denominator differs by disease, so the figures aren't always directly comparable — each carries its basis on the virus's detail card below. Rabies, Ebola, Marburg, hantavirus, Powassan and mpox are a share of clinical or reported cases (people already sick enough to be counted), which is why they run high; COVID-19, influenza and measles are a share of all symptomatic illnesses (a far larger base), which is why they run low. A blank case-fatality rate means either no figure is published on a comparable basis, or death simply isn't the main danger — Zika's risk is birth defects, RSV's is infant and older-adult hospitalization.

Compare One Metric Across All 15 Viruses

Pick a metric and see every virus lined up on the same 0–100% axis. Only metrics that share this scale are charted here — a virus with no published figure is shown as an explicit gap, and a source-reported range is drawn as a band rather than assumed as a single number.

Geography:
Metric:
Sort:
0%25%50%75%100%Rabies (US): 100%Rabies (US)100%Hantavirus (hantavirus pulmonary syndrome, US): 38%Hantavirus38%Powassan virus: 13.2%Powassan virus13.2%West Nile virus: 9.6%West Nile virus ⚠9.6%Avian influenza A(H5N1): 1.43%Avian influenza A(H5N1) ⚠1.43%COVID-19 (SARS-CoV-2): 0.2–0.51%COVID-19 (SARS-CoV-2)0.2–0.51%Dengue: 0.2%Dengue0.2%Measles: 0.13%Measles ⚠0.13%Seasonal influenza: 0.09%Seasonal influenza0.09%Mpox (monkeypox): 0.04%Mpox (monkeypox) ⚠0.04%Ebola virus disease: Data not availableEbola virus disease ⚠Not present in the USMarburg virus disease: Data not availableMarburg virus diseaseNot present in the USNorovirus: Data not availableNorovirusData not availableRespiratory syncytial virus (RSV): Data not availableRespiratory syncytial virus (RSV)Data not availableZika virus: Data not availableZika virusData not available

Reported figure Reported range (min–max, not a point estimate) Data not available (not shown as zero) Evolving situation — figures can shift within weeks

Interactive Comparison

Sort by any funnel stage, or hide viruses you don't want to compare.

Geography:
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Show/hide viruses (15 of 15)
United States funnel data for all 15 viruses covered by this tool.
VirusAnnual Exposure / CasesHospitalization RateCase Fatality RateAnnual DeathsData as of
Avian influenza A(H5N1)Evolving SituationEmerging in the USHigh surveillance confidence70Data not available1.43%1
COVID-19 (SARS-CoV-2)Common in the USModerate surveillance confidence10,400,000–16,700,000Data not available0.2–0.51%34,000–53,000
DengueMainly Imported into USHigh surveillance confidence1,32036.1%0.2%6
Ebola virus diseaseEvolving SituationNot Present in the USModerate surveillance confidenceData not availableData not availableData not availableData not available
Hantavirus (hantavirus pulmonary syndrome, US)Established in the USHigh surveillance confidenceData not availableData not available38%Data not available
Marburg virus diseaseNot Present in the USModerate surveillance confidenceData not availableData not availableData not availableData not available
MeaslesEvolving SituationMainly Imported into USHigh surveillance confidence2,28911%0.13%3
Mpox (monkeypox)Evolving SituationMainly Imported into USModerate surveillance confidence2,5199.5%0.04%1
NorovirusCommon in the USModerate surveillance confidence19,000,000–21,000,000Data not availableData not available900
Powassan virusEstablished in the USHigh surveillance confidence6092.2%13.2%9
Rabies (US)Established in the USHigh surveillance confidence1,400,000Data not available100%Data not available
Respiratory syncytial virus (RSV)Common in the USHigh surveillance confidence3,600,000–6,500,000Data not availableData not available10,000–23,000
Seasonal influenzaCommon in the USHigh surveillance confidence51,000,000Data not available0.09%45,000
West Nile virusEvolving SituationEstablished in the USHigh surveillance confidence1,80877%9.6%173
Zika virusMainly Imported into USHigh surveillance confidenceData not availableData not availableData not availableData not available

Full Comparison Table

Geography:
United States funnel data for all 15 viruses, listed alphabetically.
Virus Annual Exposure / CasesHospitalization RateCase Fatality RateAnnual Deaths Data as of
Avian influenza A(H5N1) Evolving Situation Emerging in the US 70 Data not available 1.43% 1 2026-03-06
COVID-19 (SARS-CoV-2) Common in the US 10,400,000–16,700,000 Data not available 0.2–0.51% 34,000–53,000 2026-02-19
Dengue Mainly Imported into US 1,320 36.1% 0.2% 6 2026-09-09
Ebola virus disease Evolving Situation Not Present in the US Data not available Data not available Data not available Data not available 2026-09-12
Hantavirus (hantavirus pulmonary syndrome, US) Established in the US Data not available Data not available 38% Data not available 2026-09-15
Marburg virus disease Not Present in the US Data not available Data not available Data not available Data not available 2026-01-29
Measles Evolving Situation Mainly Imported into US 2,289 11% 0.13% 3 2026-08-06
Mpox (monkeypox) Evolving Situation Mainly Imported into US 2,519 9.5% 0.04% 1 2026-08-27
Norovirus Common in the US 19,000,000–21,000,000 Data not available Data not available 900 2024-05-08
Powassan virus Established in the US 60 92.2% 13.2% 9 2026-06-02
Rabies (US) Established in the US 1,400,000 Data not available 100% Data not available 2026-02-10
Respiratory syncytial virus (RSV) Common in the US 3,600,000–6,500,000 Data not available Data not available 10,000–23,000 2026-02-19
Seasonal influenza Common in the US 51,000,000 Data not available 0.09% 45,000 2026-03-12
West Nile virus Evolving Situation Established in the US 1,808 77% 9.6% 173 2026-07-24
Zika virus Mainly Imported into US Data not available Data not available Data not available Data not available 2026-06-16
Global (WHO) funnel data for all 15 viruses, listed alphabetically.
Virus Annual Exposure / CasesSevere Outcome RateCase Fatality RateAnnual Deaths Data as of
Avian influenza A(H5N1) Evolving Situation Emerging in the US 30 Data not available 40% 12 2026-08-07
COVID-19 (SARS-CoV-2) Common in the US Data not available Data not available Data not available Data not available 2026-08-30
Dengue Mainly Imported into US 100,000,000–400,000,000 Data not available Data not available 12,000+ 2024-12-31
Ebola virus disease Evolving Situation Not Present in the US Data not available Data not available 25–90% Data not available 2025-04-24
Hantavirus (hantavirus pulmonary syndrome, US) Established in the US Data not available Data not available Data not available Data not available 2026-05-06
Marburg virus disease Not Present in the US Data not available Data not available 24–88% Data not available 2025-01-20
Measles Evolving Situation Mainly Imported into US Data not available Data not available Data not available 95,000 2024-12-31
Mpox (monkeypox) Evolving Situation Mainly Imported into US Data not available Data not available Data not available Data not available 2024-08-31
Norovirus Common in the US 685,000,000 Data not available Data not available 212,489 2025-04-23
Powassan virus Established in the US Data not available Data not available Data not available Data not available —
Rabies (US) Established in the US Data not available Data not available 100% 59,000 2024-06-05
Respiratory syncytial virus (RSV) Common in the US Data not available Data not available Data not available Data not available 2025-12-19
Seasonal influenza Common in the US 1,000,000,000 Data not available Data not available 290,000–650,000 2025-02-28
West Nile virus Evolving Situation Established in the US Data not available 0.67% Data not available Data not available 2017-10-03
Zika virus Mainly Imported into US Data not available Data not available Data not available Data not available 2025-11-06

How a Figure Changes Over Time

Each figure on this page carries a dated history so a reader can watch it move over time. Several series now trace a real multi-year trend: US measles cases run across ten years of CDC annual counts (elimination-era lows to the 2025 resurgence), West Nile virus cases and deaths across nine years of ArboNET data, Powassan virus's steady decade-long climb, seasonal-flu illnesses and deaths across eight CDC burden seasons, and COVID-19 deaths as two honestly-separate NCHS death-certificate series. Where a metric is a single standing estimate or has no comparable multi-year series published — norovirus's annual burden, or a rate an agency reports only once — it is shown honestly as one point rather than a fabricated slope, and grows into a line as figures are re-checked. Every point links back to its primary source.

06251.3k1.9k2.5k2016-12-31: 86862017-12-31: 1201202018-12-31: 3813812019-12-31: 1,2741,2742020-12-31: 13132021-12-31: 49492022-12-31: 1211212023-12-31: 59592024-12-31: 2852852025-12-31: 2,2892,2892016-12-312017-12-312018-12-312019-12-312020-12-312021-12-312022-12-312023-12-312024-12-312025-12-31
Data points & sources (10)
  1. 2016-12-31: 86 — CDC — Measles Cases and Outbreaks (tier1)
  2. 2017-12-31: 120 — CDC — Measles Cases and Outbreaks (tier1)
  3. 2018-12-31: 381 — CDC — Measles Cases and Outbreaks (tier1)
  4. 2019-12-31: 1,274 — CDC — Measles Cases and Outbreaks (tier1)
  5. 2020-12-31: 13 — CDC — Measles Cases and Outbreaks (tier1)
  6. 2021-12-31: 49 — CDC — Measles Cases and Outbreaks (tier1)
  7. 2022-12-31: 121 — CDC — Measles Cases and Outbreaks (tier1)
  8. 2023-12-31: 59 — CDC — Measles Cases and Outbreaks (tier1)
  9. 2024-12-31: 285 — CDC — Measles Cases and Outbreaks (tier1)
  10. 2025-12-31: 2,289 — CDC — Measles Cases and Outbreaks (tier1)

Virus-by-Virus Detail

COVID-19 (SARS-CoV-2)

A respiratory illness caused by the SARS-CoV-2 coronavirus and spread mainly through the air; most cases are mild, but it can cause severe pneumonia, especially in older adults and people with underlying conditions.

Common in the US Circulates year-round across the US and is one of the country's leading causes of respiratory hospitalization and death.

COVID-19 (SARS-CoV-2) risk snapshot chart — severe outcome, hospitalization, and case fatality rates

United States

  • Annual Exposure / Cases 10,400,000–16,700,000
  • Hospitalization Rate Data not available
  • Case Fatality Rate 0.2–0.51% Of symptomatic illnesses (2024–25 modeled season); varies widely by variant, age, and vaccination.
  • Annual Deaths 34,000–53,000

Source: CDC MMWR — Respiratory Virus Activity, United States, July 1, 2024–June 30, 2025 · Data as of 2026-02-19 · Surveillance confidence: moderate

Illness/hospitalization/death figures are Oct 1, 2024–Jul 5, 2025 modeled range estimates; COVID-19 is no longer nationally notifiable, so no clean confirmed-case count exists. cases_per_100k is left UNAVAILABLE. case_fatality_rate_pct is now shown as a BOUNDING RANGE (0.2-0.5%) rather than a point: the low bound is the smallest deaths / largest illnesses and the high bound the reverse, so it honestly spans the uncertainty in the two published ranges instead of inventing a single pairing. The 'How a figure changes over time' trend for COVID shows two honestly-separate NCHS death-certificate series (they must not be merged): deaths involving COVID-19 (underlying or contributing) — 377,883 (2020), 460,513 (2021), 244,986 (2022), 76,446 (2023) — and the narrower underlying-cause-only count — 345,323 (2020), 415,399 (2021), 186,702 (2022), 49,928 (2023). Both use a different method than the current-season modeled figure shown as the live value, so they are not directly comparable to it.

Global (WHO)

WHO's dashboard counts 7,116,554 deaths and 779,366,737 cases reported to WHO cumulatively through 30 August 2026. Those are cumulative totals, and the annual slices are not comparable to the US single-season figures: only 26,889 deaths were reported to WHO for calendar year 2025, from 46 of 240 reporting countries and areas, because global COVID-19 surveillance has wound down — the annual global cells are therefore left UNAVAILABLE rather than charted as a misleading side-by-side. For scale, WHO estimates about 14.9 million excess deaths were associated with the pandemic worldwide in 2020–2021 (range 13.3–16.6 million; WHO news release, 5 May 2022), far more than the deaths officially reported over that period.

Source: WHO — COVID-19 dashboard: deaths reported to WHO (data through 30 August 2026) · Data as of 2026-08-30 · Surveillance confidence: low

How each COVID-19 figure was sourced and calculated →

Read the full CoronavirusQuestions.com risk snapshot →

Ebola virus disease

A rare but often deadly viral hemorrhagic fever spread through contact with the body fluids of infected people or animals; outbreaks occur mainly in Central and West Africa.

Not Present in the US Not present in the US — the only US cases ever (2014) were travel-associated, and risk to the US public is very low.

Evolving situation: Active WHO-declared PHEIC outbreak (Bundibugyo virus) in DRC, 7,200 confirmed cases and 3,475 confirmed deaths as of September 12, 2026 (CDC page dated September 14; Uganda's linked outbreak is over); zero cases reported in the US, CDC risk to the general US public assessed as low (updated September 8, 2026).

Ebola virus disease risk snapshot chart — severe outcome, hospitalization, and case fatality rates

United States

No US-specific figures — this virus is not established in the United States (see the note above). Its global severity is in the Global (WHO) column.

Source: CDC — Ebola Outbreak: Current Situation · Data as of 2026-09-12 · Surveillance confidence: moderate

Ebola is not endemic in the United States and has no annual US case count — the only US cases on record were a handful of imported/travel-associated infections in 2014. The active outbreak CDC is tracking (7,200 confirmed cases in DRC as of September 12, 2026) is abroad, so US annual exposure/cases is UNAVAILABLE rather than a domestic figure; see Global (WHO) for the disease's case-fatality range. The Bundibugyo species has two prior outbreaks (Uganda 2007, DRC 2012); CDC's outbreak history page (reviewed May 29, 2026) gives 32% and 55%, WHO gives 30% and 50%, and the pooled estimate is 32.8% (95% CI 25.8–40.2) — a species characteristic rather than a US rate, and the 2026 outbreak's crude CFR (~48%) sits above it.

Global (WHO)

  • Annual Exposure / Cases Data not available
  • Severe Outcome Rate Data not available
  • Case Fatality Rate 25–90% Of Ebola cases; WHO average ~50%, ranging 25–90% across outbreaks.
  • Annual Deaths Data not available

Source: WHO — Ebola virus disease fact sheet · Data as of 2025-04-24 · Surveillance confidence: moderate

WHO puts the average Ebola case fatality rate at about 50%, ranging 25–90% across past outbreaks. Ebola cases and deaths are outbreak-driven rather than an annual global figure, so they are left UNAVAILABLE. Fact sheet re-read 2026-09-15: dated 24 April 2025 (the date now carried here) and unchanged — still "around 50%", 25–90% across outbreaks; the current Bundibugyo outbreak's crude figure is on the US-scope record.

Read the full EbolaQuestions.com risk snapshot →

Hantavirus (hantavirus pulmonary syndrome, US)

A group of viruses spread chiefly by breathing in air contaminated with infected rodent droppings, urine, or saliva; in the Americas it can cause hantavirus pulmonary syndrome, a severe and sometimes fatal lung disease.

Established in the US A rare US disease — roughly a few dozen cases a year — concentrated in the rural western states.

Hantavirus (hantavirus pulmonary syndrome, US) risk snapshot chart — severe outcome, hospitalization, and case fatality rates

United States

  • Annual Exposure / Cases Data not available
  • Hospitalization Rate Data not available
  • Case Fatality Rate 38% Of people who develop respiratory symptoms (CDC's About Hantavirus page). CDC's surveillance page separately reports 35% across all 890 laboratory-confirmed hantavirus disease cases 1993–2023, including 31 non-pulmonary infections; the 38% is kept here because it describes clinical HPS, the syndrome this record is about.
  • Annual Deaths Data not available

Source: CDC — Reported Cases of Hantavirus Disease · Data as of 2026-09-15 · Surveillance confidence: high

CDC's own page (dated 2026-04-23) reports only a cumulative total (890 cases, 1993-2023; 859 HPS + 31 non-pulmonary), not a clean single-year annual figure, so annual_exposure_or_cases_estimate is UNAVAILABLE rather than substituting the cumulative number. CDC's weekly NNDSS tables give provisional annual HPS counts — 20 in 2024, 38 in 2025 — but year-end provisional counts are routinely revised upward by a third or more, so they are not used as an annual figure either. case_fatality_rate_pct (38%) is specifically for hantavirus pulmonary syndrome once respiratory symptoms develop. severe_outcome_rate_pct/hospitalization_rate_pct left UNAVAILABLE after a Phase B literature search: HPS by clinical case definition already involves respiratory failure, so a distinct 'hospitalization rate' may not be a meaningful CDC/literature statistic; the only figure found (67% required mechanical ventilation) came from a 12-patient pediatric case series, too narrow to represent the general population.

Global (WHO)

WHO estimates 10,000 to over 100,000 hantavirus infections worldwide each year, with the largest burden in Asia and Europe — where the illness is haemorrhagic fever with renal syndrome (HFRS), carrying a case-fatality rate of under 1% to 15%. The Americas (including the US) report only hundreds of cases a year, but of the more severe hantavirus pulmonary syndrome (HPS/HCPS), whose case-fatality rate runs about 20–40%. Because the worldwide total mixes these two clinically distinct syndromes, WHO publishes no single comparable annual global figure, so the global cells are left unavailable; the US column above is HPS-specific.

Source: WHO — Hantavirus fact sheet · Data as of 2026-05-06 · Surveillance confidence: low

Read the full HantavirusQuestions.com risk snapshot →

Norovirus

A highly contagious virus that causes vomiting and diarrhea (gastroenteritis), spread through contaminated food, water, surfaces, or close contact; it is the most common cause of foodborne illness in the United States.

Common in the US The most common cause of foodborne illness in the US, with an estimated 19–21 million cases a year.

Norovirus risk snapshot chart — severe outcome, hospitalization, and case fatality rates

United States

  • Annual Exposure / Cases 19,000,000–21,000,000
  • Hospitalization Rate Data not available
  • Case Fatality Rate Data not available
  • Annual Deaths 900

Source: CDC — Norovirus Facts and Stats · Data as of 2024-05-08 · Surveillance confidence: moderate

CDC's current published US burden estimate (Norovirus Facts and Stats, updated 2024-05-08): about 900 deaths a year, mostly among adults aged 65 and older, and 19-21 million illnesses. This supersedes the older 570-800 death estimate from CDC's 2013 Emerging Infectious Diseases synthesis. Page re-read 2026-09-15: still dated May 8, 2024 with the same figures (it also gives 109,000 hospitalizations and 465,000 emergency-department visits a year), so the 2024-05-08 date stands as the figure's own date. Norovirus is not individually case-reportable, so the case-fatality and hospitalization rates are left UNAVAILABLE rather than derived as crude ratios of two modelled estimates.

Global (WHO)

  • Annual Exposure / Cases 685,000,000 peer-reviewed estimate Modeled global estimate: ~685 million norovirus cases per year (95% CI 491 million–1.1 billion); ~85% of illnesses occur in developing countries. Re-read 2026-09-15: still the latest published global estimate (CDC's Facts and Stats page, May 8, 2024, cites the same study).
  • Severe Outcome Rate Data not available
  • Case Fatality Rate Data not available
  • Annual Deaths 212,489 peer-reviewed estimate Modeled global estimate: ~212,489 norovirus deaths per year (95% CI 160,595–278,420); ~99% occur in developing countries. Re-read 2026-09-15: still the latest published global estimate (CDC's Facts and Stats page, May 8, 2024, cites the same study).

Source: CDC Yellow Book 2026 — Norovirus · Data as of 2025-04-23 · Surveillance confidence: low

CDC's Yellow Book (2026 edition, page updated April 23, 2025) reports that globally norovirus causes approximately 18% of acute gastroenteritis cases and is responsible for tens of thousands of deaths annually, without a precise count. The two populated cells are therefore the modelled estimates from Bartsch et al. 2016 (Tier 2): ~685 million cases and ~212,489 deaths a year. CDC's Norovirus Facts and Stats page (May 8, 2024) cites the same 685 million cases and about 50,000 child deaths. Re-read 2026-09-15: no newer global estimate has been published by CDC or WHO, so the 2016 figures and their dates stand.

Read the full NorovirusQuestions.com risk snapshot →

Measles

A highly contagious virus that spreads through the air and causes fever and a distinctive rash; it can lead to serious complications such as pneumonia and brain swelling, and is preventable by vaccine.

Mainly Imported into US Eliminated in the US in 2000, but imported cases now drive outbreaks — 2,288 US cases in 2025.

Evolving situation: Largest US measles resurgence since 1992 (2,288 confirmed cases, full-year 2025); 2026 already at 2,134 confirmed cases as of June 25, 2026.

Measles risk snapshot chart — severe outcome, hospitalization, and case fatality rates

United States

  • Annual Exposure / Cases 2,289
  • Hospitalization Rate 11%
  • Case Fatality Rate 0.13% Of reported US measles cases (2025: 3 deaths per 2,289 cases).
  • Annual Deaths 3

Source: CDC — Measles Cases and Outbreaks · Data as of 2026-08-06 · Surveillance confidence: high

annual_exposure_or_cases_estimate and annual_deaths_estimate are full-year 2025 confirmed totals. hospitalization_rate_pct (11%) is from the CDC MMWR Jan-Apr 2025 update, the most specific percentage CDC published. case_fatality_rate_pct is a same-record derivation (deaths ÷ cases, both CDC full-year 2025 US totals) per the tiered-sourcing/derivation policy (SITE-PLAYBOOK.md §12a) — previously left UNAVAILABLE when derivation from raw CDC figures wasn't yet permitted. As of August 6, 2026, 2,465 measles cases had already been reported in 2026 — already exceeding the full 2025 total and on pace for the worst year since elimination. 2026 is an incomplete year and is not yet shown in the trend.

Global (WHO)

  • Annual Exposure / Cases Data not available
  • Severe Outcome Rate Data not available
  • Case Fatality Rate Data not available
  • Annual Deaths 95,000

Source: WHO — Measles fact sheet · Data as of 2024-12-31 · Surveillance confidence: moderate

WHO estimates 95,000 measles deaths globally in 2024 (down from 780,000 in 2000). WHO's fact sheet states no global annual case total, so global cases and rates are left UNAVAILABLE. Fact sheet re-read 2026-09-15: re-dated 15 July 2026 but 2024 (95,000 deaths) is still the latest year estimated — WHO's 2025 estimate is expected with the next annual measles report — so the 2024 figure and its date stand.

How each Measles figure was sourced and calculated →

Mpox (monkeypox)

A viral disease (formerly called monkeypox) that causes a painful or itchy rash along with flu-like symptoms, spread mainly through close skin-to-skin contact.

Mainly Imported into US Established low-level US transmission after the 2022 outbreak; cases continue at a much lower level.

Evolving situation: CDC's situation summary (August 27, 2026) still frames both clades as active: since November 2024 there have been more than 50 laboratory-confirmed clade I cases in the United States (almost all subclade Ib, travel-linked, no deaths), with autochthonous clade Ib transmission reported in Western Europe from fall 2025 and CDC expecting additional US cases; clade II continues at low levels, with fall 2025 the highest monthly counts since the 2022 peak before returning to background by December 2025. Risk to most people in the United States remains low.

Mpox (monkeypox) risk snapshot chart — severe outcome, hospitalization, and case fatality rates

United States

  • Annual Exposure / Cases 2,519 Reported US MPXV infections in calendar year 2025 (2024: 2,803), from the One CDC Data Platform and NNDSS. Includes 10 travel-associated clade Ib cases; genomic surveillance attributed ~97.5% of sequences to descendants of the 2022 clade IIb outbreak lineage.
  • Hospitalization Rate 9.5% Of the 4,635 US cases in 2024–2025 (87.0% of all cases) with hospitalization status reported; CDC states the rate did not differ by year. 2.0% among vaccinated patients; unvaccinated patients had 9.73 times the odds of hospitalization.
  • Case Fatality Rate 0.04% Of reported US cases in 2025 — one death among 2,519 cases, as stated by CDC (2024: 0.18%, five deaths among 2,803). Deaths are those confirmed by the jurisdiction as attributed to MPXV. No US clade Ib deaths have been reported. The 2022–23 outbreak figure this replaces was 0.13% (clade IIb; ~94% of deaths in severely immunocompromised people).
  • Annual Deaths 1 Deaths confirmed by jurisdictions as attributed to MPXV in 2025 (2024: 5).

Source: CDC — Monkeypox in the United States and Around the World: Current Situation (updated August 27, 2026) · Data as of 2026-08-27 · Surveillance confidence: moderate

All five US cells now come from CDC's MMWR surveillance summary for 2024–2025 (published August 20, 2026): 2,519 cases, 1 death and a 0.04% fatality proportion for 2025, and a 9.5% hospitalization proportion for 2024–2025 combined among cases with known status. severe_outcome_rate_pct stays UNAVAILABLE — CDC publishes no severe-illness proportion for the general US case population, only the hospitalization proportion above. cases_per_100k is a Tier 1.5 derivation (CDC 2025 case count ÷ US Census Vintage 2025 population) per SITE-PLAYBOOK.md §12a. Until this MMWR, CDC's case-data page was dashboard-rendered without a static annual total, which is why these cells were previously UNAVAILABLE.

Global (WHO)

In the global outbreak from January 2022 to August 2024, over 100,000 laboratory-confirmed mpox cases and over 220 deaths were reported across 120+ countries. This is a cumulative multi-year outbreak total, not an annual rate, so funnel figures are UNAVAILABLE. Fact sheet re-read 2026-09-15: still dated 26 August 2024 and still the latest WHO fact-sheet figure. CDC's situation summary (August 27, 2026) puts the clade IIb outbreak at more than 100,000 cases in 122 countries and gives clade-specific death rates from recent outbreaks — under 0.5% (clade Ib), about 3% (clade Ia), under 0.1% (clade II) — which are ranges by clade rather than one comparable global fatality figure, so the CFR cell also stays UNAVAILABLE.

Source: WHO — Mpox fact sheet · Data as of 2024-08-31 · Surveillance confidence: moderate

How each Mpox figure was sourced and calculated →

Powassan virus

A rare tick-borne virus found in North America that can cause encephalitis (brain inflammation); most infections cause no symptoms, but severe cases can be life-threatening.

Established in the US A rare US tick-borne disease — tens of cases a year — mainly in the Northeast and Great Lakes regions.

Powassan virus risk snapshot chart — severe outcome, hospitalization, and case fatality rates

United States

  • Annual Exposure / Cases 60 Final 2024 reported Powassan cases (all disease cases). CDC's page, re-read 2026-09-15 (updated June 3, 2026, data current as of June 2, 2026), still marks 2025 (76 cases) as preliminary and subject to change, so 2024 remains the latest final year. Most Powassan infections are asymptomatic and never reported, so this counts diagnosed cases, not all infections.
  • Hospitalization Rate 92.2% Of reported US cases, 2004–2025 (CDC's own hospitalizations-by-year series, which it now publishes on this page). 2024 alone: 60 of 60 reported cases hospitalized. Replaces the Tier 2 figure of 91.7% (Kakoullis et al. 2023, 264 of 288 published cases 2004–2022), kept as the earlier history point. Because only neuroinvasive Powassan disease is reliably reported, this reflects the severe end of infection, not all infections.
  • Case Fatality Rate 13.2% Of reported US cases, 2004–2025 (CDC's own deaths-by-year series). 2024 alone: 9 of 60 (15.0%); 2025 preliminary: 10 of 76. Replaces the 11% figure (a CDC 2006–2016 cohort, 11 of 99 cases), kept as the earlier history point. Reported cases are predominantly severe neuroinvasive disease, so this overstates the fatality of infection overall.
  • Annual Deaths 9 Deaths among reported US Powassan disease cases in 2024 (final; data current as of June 2, 2026). 2025 preliminary: 10.

Source: CDC — Historic Data (2004-2025), Powassan Virus, ArboNET (data current as of June 2, 2026) · Data as of 2026-06-02 · Surveillance confidence: high

case_fatality_rate_pct (13.2%) and hospitalization_rate_pct (92.2%) are §12a derivations from CDC's own ArboNET totals for all reported US Powassan disease cases 2004–2025 (63 deaths and 439 hospitalizations among 476 cases; data current as of June 2, 2026), superseding the 11% CDC 2006–2016 cohort figure and the 91.7% Tier 2 systematic-review figure, both retained as earlier history points. annual_deaths_estimate is the 2024 final count (9). severe_outcome_rate_pct left UNAVAILABLE: Powassan neuroinvasive disease is the only form nationally notifiable, so any 'severe outcome' percentage drawn from this surveillance stream would reflect ascertainment bias (mild/non-neuroinvasive infections are essentially never captured) rather than a true population rate.

How each Powassan virus figure was sourced and calculated →

Respiratory syncytial virus (RSV)

Respiratory syncytial virus, a common seasonal respiratory virus that usually causes mild, cold-like symptoms but can be serious for infants and older adults.

Common in the US Circulates each US respiratory season and is a leading cause of hospitalization in infants and older adults.

Respiratory syncytial virus (RSV) risk snapshot chart — severe outcome, hospitalization, and case fatality rates

United States

  • Annual Exposure / Cases 3,600,000–6,500,000
  • Hospitalization Rate Data not available
  • Case Fatality Rate Data not available
  • Annual Deaths 10,000–23,000

Source: CDC MMWR — Respiratory Virus Activity, United States, July 1, 2024–June 30, 2025 · Data as of 2026-02-19 · Surveillance confidence: high

annual_exposure_or_cases_estimate is outpatient visits (Oct 1, 2024-May 3, 2025), the closest CDC equivalent to a case estimate since RSV isn't individually notifiable; hospitalizations were 190,000-350,000 in the same window. hospitalization_rate_pct was considered for derivation in Phase B (SITE-PLAYBOOK.md §12a) but deliberately left UNAVAILABLE: both the hospitalization count and the outpatient-visit denominator are ranges with no stated low/high pairing, so a derived rate would require inventing a pairing method CDC doesn't specify.

Global (WHO)

WHO estimates RSV caused 3.6 million hospitalizations and about 100,000 deaths in children under 5 worldwide in 2019. These cover young children only, not an all-ages annual rate comparable to the US figures, so funnel cells are UNAVAILABLE. Fact sheet re-read 2026-09-15: re-dated 19 December 2025 (the date now carried here) and still citing the same under-5 figures, which trace to 2019 modelling (Li et al., Lancet 2022); WHO states global adult RSV burden is not known.

Source: WHO — Respiratory syncytial virus (RSV) fact sheet · Data as of 2025-12-19 · Surveillance confidence: moderate

Seasonal influenza

The seasonal flu, a contagious respiratory illness caused by influenza viruses that circulate each winter; it ranges from mild to severe and is preventable by annual vaccination.

Common in the US Circulates every US winter, causing tens of millions of illnesses and tens of thousands of deaths a year.

Seasonal influenza risk snapshot chart — severe outcome, hospitalization, and case fatality rates

United States

  • Annual Exposure / Cases 51,000,000
  • Hospitalization Rate Data not available
  • Case Fatality Rate 0.09% Of symptomatic illnesses (CDC modeled burden).
  • Annual Deaths 45,000

Source: CDC — 2024-2025 Influenza Season Summary: Severity, Disease Burden, and Burden Prevented · Data as of 2026-03-12 · Surveillance confidence: high

2024-25 was classified 'high severity' — the most severe season since 2017-18. CDC's own long-run range (2010-2025) is 9.4M-51M illnesses and 6,300-52,000 deaths, so this single season sits at the top of that range. case_fatality_rate_pct is a same-record derivation (deaths ÷ illnesses, both CDC 2024-25-season modeled estimates) per SITE-PLAYBOOK.md §12a; both inputs are model-based CDC burden estimates, not raw notified counts, since seasonal influenza isn't individually reportable. The illnesses and deaths trends use CDC's modeled disease-burden estimates (same method each season), one point per season from 2017-18 through 2024-25 — deaths: 52,000 (2017-18), 28,000 (2018-19), 22,000 (2019-20), 6,300 (2021-22), 21,000 (2022-23), 28,000 (2023-24), 45,000 (2024-25). The 2020-21 season is intentionally absent: CDC published no burden estimate for it because influenza circulation was minimal under COVID-19 mitigation. These modeled burden figures are NOT the smaller coded death-certificate counts, which are a different series and are not mixed in.

Global (WHO)

  • Annual Exposure / Cases 1,000,000,000
  • Severe Outcome Rate Data not available
  • Case Fatality Rate Data not available
  • Annual Deaths 290,000–650,000

Source: WHO — Influenza (seasonal) fact sheet · Data as of 2025-02-28 · Surveillance confidence: moderate

WHO estimates ~1 billion seasonal influenza cases worldwide each year, including 3–5 million cases of severe illness and 290,000–650,000 respiratory deaths. Fact sheet re-read 2026-09-15: dated 28 February 2025 (the date now carried here) and unchanged — the ~1 billion cases and 290,000–650,000 deaths are WHO's standing estimates, restated rather than re-derived.

How each Seasonal influenza figure was sourced and calculated →

Zika virus

A mosquito-borne virus that usually causes mild or no symptoms in adults but can cause serious birth defects when a woman is infected during pregnancy.

Mainly Imported into US Seen mainly in US travelers; the local 2016–17 Florida and Texas transmission has since subsided.

Zika virus risk snapshot chart — severe outcome, hospitalization, and case fatality rates

United States

No US-specific figures — this virus is not established in the United States (see the note above). Its global severity is in the Global (WHO) column.

Source: CDC — Zika Cases in the United States · Data as of 2026-06-16 · Surveillance confidence: high

CDC states no local mosquito-borne Zika transmission has been reported in the continental US since 2018, and no confirmed cases from US territories since 2019. The case-count table on this page could not be extracted as a clean static annual figure with certainty, so funnel fields are UNAVAILABLE rather than guessed.

Global (WHO)

WHO reports Zika transmission in 92 countries and territories and estimates 5–15% of infants born to women infected during pregnancy have Zika-related complications. No global annual case or death count is published, so funnel figures are UNAVAILABLE. Fact sheet re-read 2026-09-15: re-dated 6 November 2025 (the date now carried here); it still publishes no global annual case or death count (92 countries and territories with mosquito-borne transmission; surveillance limited).

Source: WHO — Zika virus fact sheet · Data as of 2025-11-06 · Surveillance confidence: low

West Nile virus

The leading mosquito-borne virus in the continental United States; most infected people have no symptoms, but a small share develop serious neurological illness.

Established in the US The leading mosquito-borne virus in the continental US, though most infections cause no symptoms and only a small share are severe.

Evolving situation: 2023 figures (2,770 cases, 95% West Nile) are the most recent finalized full-year CDC data; the 2025 season was tracking at 771 cases (490 neuroinvasive) as of Sept 9, 2025 per preliminary ArboNET data, but that season total was not yet finalized as of this research.

West Nile virus risk snapshot chart — severe outcome, hospitalization, and case fatality rates

United States

  • Annual Exposure / Cases 1,808
  • Hospitalization Rate 77% Of reported WNV cases (1,396 of 1,808 hospitalized); reported cases skew severe (91% neuroinvasive), so this is not a share of all infections.
  • Case Fatality Rate 9.6% Of reported WNV cases (173 of 1,808 died; 91% of cases were neuroinvasive). Among neuroinvasive cases specifically the CFR is ~13%. Most WNV infections are mild or asymptomatic and never reported.
  • Annual Deaths 173

Source: CDC MMWR — West Nile Virus and Other Nationally Notifiable Arboviral Diseases, United States, 2024 · Data as of 2026-07-24 · Surveillance confidence: high

Figures are West Nile virus–specific (ArboNET). WNV caused 1,808 reported US human cases in 2024 (92% of all notifiable arboviral disease) with 173 deaths; 91% of reported cases were neuroinvasive (the severe form). Case-fatality and hospitalization rates here are therefore among REPORTED cases, which skew severe — an estimated 80% of WNV infections are asymptomatic and never counted. Reported WNV cases swing widely year to year with mosquito activity.

Global (WHO)

  • Annual Exposure / Cases Data not available
  • Severe Outcome Rate 0.67%
  • Case Fatality Rate Data not available
  • Annual Deaths Data not available

Source: WHO — West Nile virus fact sheet · Data as of 2017-10-03 · Surveillance confidence: moderate

WHO reports that about 80% of West Nile infections are asymptomatic and roughly 1 in 150 (~0.67%) develop severe neuroinvasive disease. No global annual case or death count is published. Fact sheet re-read 2026-09-15: it is dated 3 October 2017 — older than the 2024-12-31 previously recorded here, so the date is corrected backwards to the sheet's own date. WHO has published no newer West Nile fact sheet; the ~1-in-150 severe-disease proportion is a standing figure CDC also states.

How each West Nile virus figure was sourced and calculated →

Dengue

A mosquito-borne viral infection common in tropical and subtropical regions that causes high fever and body aches; a minority of cases progress to severe, potentially fatal dengue.

Mainly Imported into US Seen mostly in US travelers; limited local transmission occurs in Puerto Rico and parts of the Gulf Coast.

Dengue risk snapshot chart — severe outcome, hospitalization, and case fatality rates

United States

  • Annual Exposure / Cases 1,320 Calendar-year 2025 dengue cases reported to ArboNET from the 50 states and the District of Columbia: 1,239 travel-associated + 81 locally acquired = 1,320 (CDC's Cases_by_Jurisdiction historic data file, which the page's maps and CSV download expose). The same scope the 2024 MMWR figure used; the page's headline 5,373 also includes 4,053 cases in Puerto Rico, the US Virgin Islands, American Samoa, Guam and the Northern Mariana Islands, where dengue is endemic and which the US Census denominator excludes.
  • Hospitalization Rate 36.1% 2024 figure, of reported US dengue cases (MMWR, May 15, 2026). CDC's ArboNET data page publishes case counts only; no 2025 hospitalization proportion had been published when the source was re-read on 2026-09-15.
  • Case Fatality Rate 0.2% 2024 figure, of reported US dengue cases (97% travel-associated in 2024). CDC's ArboNET data page publishes case counts only; no 2025 death count or fatality proportion had been published when the source was re-read on 2026-09-15.
  • Annual Deaths 6 2024 deaths among reported US dengue cases (MMWR, May 15, 2026). CDC's ArboNET data page publishes case counts only; no 2025 death count had been published when the source was re-read on 2026-09-15.

Source: CDC — Dengue Historic Data (2010–2025), ArboNET (updated September 9, 2026) · Data as of 2026-09-09 · Surveillance confidence: high

2025 (ArboNET, states + DC): 1,320 cases, 93.9% travel-associated (1,239) and 6.1% locally acquired (81). 2024 in the same current data is 3,811 (3,706 + 105) — the MMWR published 3,798 for 2024 and that published figure is kept as the 2024 history point. Hospitalization (36.1%), deaths (6) and the fatality proportion (0.2%) remain the 2024 MMWR figures because CDC has published no 2025 equivalents; each carries its own 2026-05-15 date. cases_per_100k is a Tier 1.5 derivation (CDC 2025 case count ÷ US Census Vintage 2025 population) per SITE-PLAYBOOK.md §12a. severe_outcome_rate_pct left UNAVAILABLE: CDC's MMWR on 2010-2021 US travel-associated dengue reports severe dengue as a small proportion of cases ("<1%") but does not publish an exact percentage — forcing that qualitative language into a point estimate would overstate precision CDC itself doesn't claim.

Global (WHO)

  • Annual Exposure / Cases 100,000,000–400,000,000
  • Severe Outcome Rate Data not available
  • Case Fatality Rate Data not available
  • Annual Deaths 12,000+

Source: WHO — Dengue and severe dengue fact sheet · Data as of 2024-12-31 · Surveillance confidence: moderate

WHO estimates 100–400 million dengue infections worldwide each year. In 2024, 14.6 million cases and over 12,000 dengue-related deaths were reported to WHO — a record high; reported deaths undercount true mortality. Fact sheet re-read 2026-09-15: it is dated 21 August 2025 and 2024 is still the latest full year it reports; for 2025 it gives only a partial-year figure (over 4 million cases and over 3,000 deaths reported from 97 countries, January–July), so the 2024 figures and their date stand.

How each Dengue figure was sourced and calculated →

Rabies (US)

A virus spread through the bite of an infected animal that attacks the nervous system; it is almost always fatal once symptoms begin, but preventable with prompt post-exposure treatment.

Established in the US Endemic in US wildlife, but human deaths are very rare (a few per year) thanks to prompt post-exposure treatment.

Rabies (US) risk snapshot chart — severe outcome, hospitalization, and case fatality rates

United States

  • Annual Exposure / Cases 1,400,000
  • Hospitalization Rate Data not available
  • Case Fatality Rate 100% Of clinical rabies cases — virtually 100% fatal once symptoms appear (not the 1.4M annual exposure evaluations).
  • Annual Deaths Data not available

Source: CDC — Rabies in the United States: Protecting Public Health · Data as of 2026-02-10 · Surveillance confidence: high

annual_exposure_or_cases_estimate (1.4 million) is Americans who seek healthcare for a possible rabies exposure annually; of these, 100,000 receive post-exposure prophylaxis. CDC states deaths are 'fewer than 10' per year rather than a precise figure, and states the disease is 'nearly 100%' fatal without timely PEP once symptoms begin — both left as qualitative CDC language rather than forced into a point-estimate percentage.

Global (WHO)

  • Annual Exposure / Cases Data not available
  • Severe Outcome Rate Data not available
  • Case Fatality Rate 100% Of clinical rabies cases — virtually 100% fatal once symptoms appear.
  • Annual Deaths 59,000

Source: WHO — Rabies fact sheet · Data as of 2024-06-05 · Surveillance confidence: moderate

WHO estimates ~59,000 human rabies deaths worldwide each year (~99% dog-mediated; ~95% in Asia and Africa). Rabies is virtually 100% fatal once clinical symptoms appear. The 59,000 figure is a standing modelled estimate. Fact sheet re-read 2026-09-15: dated 5 June 2024 (the date now carried here); it still states an estimated 59,000 deaths a year and 100% fatality once symptoms appear, and gives no newer estimate.

Avian influenza A(H5N1)

A type of bird flu (influenza A H5N1) that mainly infects birds and some mammals; human cases are rare and usually linked to close contact with infected animals, but can be severe.

Emerging in the US An emerging US situation: human cases are rare and tied to close contact with infected animals, with no sustained person-to-person spread.

Evolving situation: CDC's current situation summary (March 6, 2026) still describes an ongoing situation: A(H5) is widespread in wild birds and causing outbreaks in poultry and US dairy cows, with sporadic human cases in farm workers; CDC rates the current public health risk as low and reports no person-to-person spread. On July 7, 2025 CDC folded bird-flu updates into its routine influenza reporting. The last US H5N1 human case had onset in February 2025; the one later US A(H5) case (November 2025) was the world's first human A(H5N5) infection and was fatal. Global historical H5N1 mortality is around 50%, but US cases have been overwhelmingly mild by comparison.

Avian influenza A(H5N1) risk snapshot chart — severe outcome, hospitalization, and case fatality rates

United States

  • Annual Exposure / Cases 70
  • Hospitalization Rate Data not available
  • Case Fatality Rate 1.43% Of reported US H5N1 cases in the 2024–25 outbreak; most were mild farm-worker infections. Re-verified 2026-09-15 against CDC's current situation summary (March 6, 2026): no further H5N1 cases or deaths since the March 2025 inputs. CDC's page now counts all A(H5) subtypes — 71 cases and 2 deaths — because the 71st case (Washington, November 2025, fatal) was an A(H5N5) infection (WHO DON 590), which sits outside this H5N1 record.
  • Annual Deaths 1

Source: CDC — A(H5) Bird Flu: Current Situation (updated March 6, 2026) · Data as of 2026-03-06 · Surveillance confidence: high

70 is a cumulative outbreak total (April 2024 onward) rather than a clean annual figure. CDC's situation summary (updated March 6, 2026) reports 71 A(H5) cases and 2 deaths since February 2024 across all H5 subtypes; one of those — the November 2025 Washington case — was confirmed as A(H5N5), not H5N1 (WHO DON 590, 5 December 2025), so the H5N1 figures are 71 − 1 = 70 cases and 2 − 1 = 1 death. WHO's cumulative H5N1 table (data as of 7 August 2026) agrees: United States 67 cases / 1 death with 2024 onset, 3 / 0 in 2025, 0 in 2026. CDC's exposure breakdown of the 71: 41 dairy herds, 24 poultry farms and culling operations, 3 other animal exposure, 3 unknown. No human-to-human transmission identified. cases_per_100k and case_fatality_rate_pct are derivations per SITE-PLAYBOOK.md §12a from the March 19, 2025 CDC update — the counts have not changed since, so the inputs stand — both explicitly labelled as covering the outbreak-to-date window (not a calendar year) and, for CFR, the mild US outbreak specifically (not the far higher global historical H5N1 rate).

Global (WHO)

  • Annual Exposure / Cases 30
  • Severe Outcome Rate Data not available
  • Case Fatality Rate 40% Of WHO-confirmed cases worldwide in 2025. WHO reports only laboratory-confirmed cases, which skew heavily toward severe illness in countries where mild infections are rarely tested, so this is a reported-case fatality proportion, not an infection fatality rate. The cumulative 2003–2026 figure is 479 ÷ 1,002 = 47.8%; the mild US outbreak (1.43%) sits at the other extreme.
  • Annual Deaths 12

Source: WHO — Cumulative number of confirmed human cases for avian influenza A(H5N1) reported to WHO, 2003–2026 (data as of 7 August 2026) · Data as of 2026-08-07 · Surveillance confidence: low

WHO's cumulative table of confirmed human A(H5N1) cases (data in WHO HQ as of 7 August 2026) gives 30 cases and 12 deaths with onset in calendar year 2025 — the latest complete year — and 1,002 cases / 479 deaths in total since 2003 (for the United States it counts cases reported as A(H5) too). 2026 to 7 August: 9 cases, 2 deaths (partial year, not charted). Annual counts by onset year, 2020–2025: 1, 2, 6, 12, 81, 30 cases and 0, 1, 1, 4, 4, 12 deaths. CDC's own tally (June 26, 2026) is 1,022 cases worldwide since 1997. The WHO Influenza (avian and other zoonotic) fact sheet, re-dated 21 January 2026 and re-read 2026-09-15, still gives no precise total ("hundreds of human cases, and many deaths"), so the table is cited instead. Surveillance confidence is low: only laboratory-confirmed cases are counted and testing of mild illness varies widely by country.

How each Avian influenza A figure was sourced and calculated →

Marburg virus disease

A rare and severe viral hemorrhagic fever related to Ebola, spread through contact with infected body fluids; outbreaks are sporadic and often highly fatal.

Not Present in the US Not present in the US — no domestically acquired cases have ever been recorded; outbreaks occur abroad.

Marburg virus disease risk snapshot chart — severe outcome, hospitalization, and case fatality rates

United States

No US-specific figures — this virus is not established in the United States (see the note above). Its global severity is in the Global (WHO) column.

Source: CDC — Marburg Outbreak in Ethiopia: Current Situation · Data as of 2026-01-29 · Surveillance confidence: moderate

Marburg virus disease has never been endemic in the United States and has no annual US case count — no domestically acquired US cases have been recorded. The figures CDC is tracking come from outbreaks abroad (most recently Ethiopia), so US annual exposure/cases is UNAVAILABLE rather than a domestic figure; see Global (WHO) for the disease's case-fatality range. case_fatality_rate_pct is the WHO/CDC historical outbreak range (24–88%), a disease characteristic rather than a US rate.

Global (WHO)

  • Annual Exposure / Cases Data not available
  • Severe Outcome Rate Data not available
  • Case Fatality Rate 24–88% Of Marburg cases; WHO average ~50%, ranging 24–88% across outbreaks.
  • Annual Deaths Data not available

Source: WHO — Marburg virus disease fact sheet · Data as of 2025-01-20 · Surveillance confidence: moderate

WHO puts the average Marburg case fatality rate at about 50%, ranging 24–88% across past outbreaks. Cases and deaths are outbreak-driven rather than an annual global figure, so they are left UNAVAILABLE. Fact sheet re-read 2026-09-15: dated 20 January 2025 (the date now carried here) and unchanged — still "around 50%", 24–88% across outbreaks; it records Rwanda's first outbreak (September 2024) and Tanzania's (January 2025).

Sources & References

Written and researched by Andy Wilcox, an independent researcher not a physician — his work is the product of disciplined primary-source research drawing on 30+ years as a consultant, operating executive, and investor. Nothing here is medical advice. About the author →