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. 2025 Nov;31(11):3889-3898.
doi: 10.1038/s41591-025-03905-2. Epub 2025 Jul 25.

Human infections with highly pathogenic avian influenza A(H5N1) viruses in the United States from March 2024 to May 2025

Melissa A Rolfes #  1 , Krista Kniss #  2 , Marie K Kirby  2 , Shikha Garg  2 , Katie Reinhart  2 , C Todd Davis  2 , Erin L Murray  3 , Debra A Wadford  3 , Kathleen Harriman  3 , Sophie Zhu  3   4 , Caterina Y Liu  3 , Christina Morales  3 , Denise Lopez  5 , Laura Esbenshade  5 , Kavita K Trivedi  6 , Farrell A Tobolowsky  7 , Thi Dang  8 , Anna Unutzer  8 , Steven Krager  9 , Kaylyn Baum  10 , Emily J Curren  10 , Alexia Harrist  10 , Julie Hand  11 , Theresa Sokol  11 , Andrea Salinas  11 , Amy Bunch  11 , Danielle Haydel  12 , Nicholas Fisher  13 , Sara F Margrey  13 , Laurie Billing  13 , George Turabelidze  14 , Jessica Goswitz  14 , Leslie Kavlak  14 , Emilio Gonzales  15 , Whitney Tillman  15 , Susan Rollo  15 , Cherissa Abdul Hamid  15 , Deborah Aragon  16 , Mackenzie Owen  16 , Allison Kohnen  16 , Amy Hoehne  17 , Andy Weigel  17 , Andrew Hennenfent  17 , Victoria Sepcic  18 , Tim Southern  19 , Cindy Beard  4   20 , Ryan Scholz  21 , Sarah Present  22 , Melissa Sutton  23 , Jennifer Morse  24 , Meghan Weinberg  25 , Seth Eckel  25 , Thomas Haupt  26 , Angela Maxted  26 , Karla Potts-Shufelt  27 , Demetre C Daskalakis  28 , Lizette O Durand  2 , Feng Liu  2 , Benjamin Rambo-Martin  2 , Kristine A Lacek  2 , Julia C Frederick  2 , Jimma Liddell  2 , Natasha Burnett  2 , Lisa M Keong  2 , Juliana DaSilva  2 , Sydney R Sheffield  2 , Malania M Wilson  2 , Han Di  2 , Sabrina S Schatzman  2 , Yunho Jang  2 , A Danielle Iuliano  2 , Alexia Couture  2 , Alicia P Budd  2 , Min Z Levine  2 , Larisa V Gubareva  2 , Tom T Shimabukuro  2 , Timothy M Uyeki  2 , Vivien G Dugan  2 , Carrie Reed  2 , Sonja J Olsen  2
Affiliations

Human infections with highly pathogenic avian influenza A(H5N1) viruses in the United States from March 2024 to May 2025

Melissa A Rolfes et al. Nat Med. 2025 Nov.

Abstract

Between March 2024 and October 2024, 46 human cases of highly pathogenic avian influenza (HPAI) A(H5N1) had been detected in the United States. The persistent panzootic spread of HPAI A(H5N1) viruses and continued detection of human cases presents an ongoing threat to public health. In this study, between November 2024 and May 2025, an additional 24 cases have been reported for a total of 70 human cases of HPAI A(H5N1): 41 were exposed to dairy cows, 24 to commercial poultry, two to backyard poultry and three had an unidentified source of exposure. All sequenced viruses were clade 2.3.4.4b. Overall, 62 cases (89%) reported eye redness, 32 (46%) fever and 29 (41%) respiratory symptoms; 54 of 67 cases (81%) reported receiving antiviral treatment. Most illnesses were mild; however, four patients were hospitalized. Of the hospitalized patients, three had pneumonia and one died. No human-to-human transmission was detected. Occupational exposure to infected animals was a risk factor for HPAI A(H5N1) virus infection and the risk to the general population remains low; however, the two cases exposed to infected backyard poultry and three cases with unidentified exposures highlight that ongoing vigilance is warranted.

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Conflict of interest statement

Competing interests: The authors declare no competing interests.

Figures

Extended Data Fig. 1
Extended Data Fig. 1
States where case patients infected with influenza A(H5N1) viruses have been detected, United States, March 2024 to May 2025.
Extended Data Fig. 2
Extended Data Fig. 2
Detections of influenza A(H5N1) viruses A) in humans with exposure to dairy cows and in dairy cow herds; B) in humans with exposure to commercial poultry and detections in commercial poultry; and C) in humans with exposure to backyard poultry and reported detections in backyard poultry, United States, March 2024 to May 2025. From New England Journal of Medicine, Garg, et al., “Highly Pathogenic Avian Influenza A(H5N1) Virus Infections in Humans”, Volume No. 392, Page No. 9, Copyright © 2025 Massachusetts Medical Society. Reprinted and amended with permission. Data available from United States Department of Agriculture (livestock/dairy cows: https://www.aphis.usda.gov/livestock-poultry-disease/avian/avian-influenza/hpai-detections/hpai-confirmed-cases-livestock; and commercial/backyard flocks: https://www.aphis.usda.gov/livestock-poultry-disease/avian/avian-influenza/hpai-detections/commercial-backyard-flocks).
Extended Data Fig. 3
Extended Data Fig. 3
Reported use of personal protective equipment among case patients infected with influenza A(H5N1) viruses that were exposed to cows (n=41) or commercial poultry (n=24), United States, March 2024 to May 2025. The following personal protective equipment is recommended to reduce exposure to avian influenza A viruses from sick animals or contaminated environments in high exposure settings: NIOSH Approved® particulate respirator, fluid-resistant coveralls, safety goggles, boot covers or boots, head cover or hair cover, and disposable gloves (for further details, see https://www.cdc.gov/bird-flu/worker-safety/index.html [last updated: 6 May 2025]). In medium risk settings, the following PPE are recommended: NIOSH Approved® particulate respirator, safety goggles, and disposable gloves.
Extended Data Fig. 4
Extended Data Fig. 4
Reported use of eye protection and facemask/respira tor as personal protective equipment (PPE) among case patients infected with influenza A(H5N1) viruses that were exposed to dairy cows or involved in depopulating commercial poultry, United States, March 2024 to May 2025. The following personal protective equipment is recommended to reduce exposure to avian influenza A viruses from sick animals or contaminated environments in high exposure settings: NIOSH Approved® particulate respirator, fluid-resistant coveralls, safety goggles, boot covers or boots, head cover or hair cover, and disposable gloves (for further details, see https://www.cdc.gov/bird-flu/worker-safety/index.html [last updated: 6 May 2025]). In medium risk settings, the following PPE are recommended: NIOSH Approved® particulate respirator, safety goggles, and disposable gloves. Of note, facemasks are not a recommended level of PPE against exposure to avian influenza A viruses.
Extended Data Fig. 5
Extended Data Fig. 5
Respiratory specimens, testing results, and antiviral treatment among case patients hospitalized with influenza A(H5N1) virus infection, United States, March 2024 to May 2025.
Extended Data Fig. 6
Extended Data Fig. 6
Timeline of educational and communication activities on influenza A(H5N1) viruses initiated by CDC, United States, March 2024 to May 2025. NCFH: National Center for Farmworker Health.
Figure 1.
Figure 1.
Detections of influenza A(H5N1) viruses in humans in the United States, March 2024 to May 2025. Figure includes detections of the first 46 human cases of A(H5N1) augmented with 24 additional detections. Publication of the first 46 detections from New England Journal of Medicine, Garg, et al., “Highly Pathogenic Avian Influenza A(H5N1) Virus Infections in Humans”, Volume No. 392, Page No. 9, Copyright © 2025 Massachusetts Medical Society. Reprinted and amended with permission.
Figure 2.
Figure 2.
Reported use of personal protective equipment among case patients infected with influenza A(H5N1) viruses that were exposed to cows (n=41) or commercial poultry (n=24), United States, March 2024 to May 2025. The following personal protective equipment is recommended to reduce exposure to avian influenza A viruses from sick animals or contaminated environments in high exposure settings: NIOSH Approved® particulate respirator, fluid-resistant coveralls, safety goggles, boot covers or boots, head cover or hair cover, and disposable gloves. In medium risk settings, the following PPE are recommended: NIOSH Approved® particulate respirator, safety goggles, and disposable gloves. Reported symptoms among case patients infected with influenza A(H5N1) viruses by type of exposure, United States, March 2024 to May 2025.
Figure 3.
Figure 3.
Phylogenetic trees of the hemagglutinin genes of clade 2.3.4.4b avian influenza A(H5N1) viruses. Sequences obtained from human cases in the United States belonging to the B3.13 (A) and D1.1 or D1.3 (B) genotypes are shown in green font.
See this image and copyright information in PMC

References

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Methods-only References

    1. Centers for Disease Control and Prevention. Highly Pathogenic Avian Influenza A(H5N1) Virus: Interim Recommendations for Prevention, Monitoring, and Public Health Investigations. https://www.cdc.gov/bird-flu/prevention/hpai-interim-recommendations.html (2024); Accessed on: May 7, 2025.
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