• Shikha Garg, Katie Reinhart, Alexia Couture, Krista Kniss, C Todd Davis, Marie K Kirby, Erin L Murray, Sophie Zhu, Vit Kraushaar, Debra A Wadford, Cara Drehoff, Allison Kohnen, Mackenzie Owen, Jennifer Morse, Seth Eckel, Jessica Goswitz, George Turabelidze, Steve Krager, Anna Unutzer, Emilio R Gonzales, Cherissa Abdul Hamid, Sascha Ellington, Alexandra M Mellis, Alicia Budd, John R Barnes, Matthew Biggerstaff, Michael A Jhung, Malia Richmond-Crum, Erin Burns, Tom T Shimabukuro, Timothy M Uyeki, Vivien G Dugan, Carrie Reed, and Sonja J Olsen.
• From the Influenza Division, Centers for Disease Control and Prevention, Atlanta (S.G., K.R., A.C., K.K., C.T.D., M.K.K., S. Ellington, A.M.M., A.B., J.R.B., M.B., M.A.J., M.R.-C., E.B., T.T.S., T.M.U., V.G.D., C.R., S.J.O.); California Department of Public Health, Richmond (E.L.M., S.Z., V.K., D.A.W.); the Epidemic Intelligence Service, Centers for Disease Control and Prevention, Atlanta (S.Z., C.D.); Colorado Department of Public Health and Environment, Denver (C.D., A.K., M.O.); Mid-Michigan District Health Department, Stanton (J.M.); Michigan Department of Health and Human Services, Lansing (S. Eckel); Missouri Department of Health and Senior Services, Jefferson City (J.G., G.T.); Benton-Franklin Health District, Kennewick, WA (S.K.); Washington State Department of Health, Tumwater (A.U.); and Texas Department of State Health Services, Austin (E.R.G., C.A.H.).
• N. Engl. J. Med. 2024 Dec 31.

BackgroundHighly pathogenic avian influenza A(H5N1) viruses have caused widespread infections in dairy cows and poultry in the United States, with sporadic human cases. We describe characteristics of human A(H5N1) cases identified from March through October 2024 in the United States.MethodsWe analyzed data from persons with laboratory-confirmed A(H5N1) virus infection using a standardized case-report form linked to laboratory results from the Centers for Disease Control and Prevention influenza A/H5 subtyping kit.ResultsOf 46 case patients, 20 were exposed to infected poultry, 25 were exposed to infected or presumably infected dairy cows, and 1 had no identified exposure; that patient was hospitalized with nonrespiratory symptoms, and A(H5N1) virus infection was detected through routine surveillance. Among the 45 case patients with animal exposures, the median age was 34 years, and all had mild A(H5N1) illness; none were hospitalized, and none died. A total of 42 patients (93%) had conjunctivitis, 22 (49%) had fever, and 16 (36%) had respiratory symptoms; 15 (33%) had conjunctivitis only. The median duration of illness among 16 patients with available data was 4 days (range, 1 to 8). Most patients (87%) received oseltamivir; oseltamivir was started a median of 2 days after symptom onset. No additional cases were identified among the 97 household contacts of case patients with animal exposures. The types of personal protective equipment (PPE) that were most commonly used by workers exposed to infected animals were gloves (71%), eye protection (60%), and face masks (47%).ConclusionsIn the cases identified to date, A(H5N1) viruses generally caused mild illness, mostly conjunctivitis, of short duration, predominantly in U.S. adults exposed to infected animals; most patients received prompt antiviral treatment. No evidence of human-to-human A(H5N1) transmission was identified. PPE use among occupationally exposed persons was suboptimal, which suggests that additional strategies are needed to reduce exposure risk. (Funded by the Centers for Disease Control and Prevention.).Copyright © 2024 Massachusetts Medical Society.

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