Highly Pathogenic Avian Influenza A(H5N1) Virus Infections in Humans
Authors: Shikha Garg, Katie Reinhart, Alexia Couture, et al.
Journal: New England Journal of Medicine, 2025 Feb 27;392(9):843-854
Conclusions:
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A(H5N1) infections in the U.S. have primarily caused mild illness, mostly conjunctivitis, in adults exposed to infected animals.
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No evidence of human-to-human transmission was found.
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PPE use was suboptimal, highlighting a need for improved preventive strategies among occupationally exposed workers.
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Rapid antiviral treatment (oseltamivir) was common and may have contributed to short disease duration and mild outcomes.
Methods:
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Data Source: Standardized case-report forms and laboratory results from the CDC influenza A/H5 subtyping kit.
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Patient Inclusion: Individuals with laboratory-confirmed A(H5N1) virus infection.
Results:
Exposure & Demographics:
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Total Cases: 46
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25 cases (54%) linked to infected or suspected dairy cows
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20 cases (43%) linked to infected poultry
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1 case (2%) had no known animal exposure (detected via routine surveillance)
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Median age of exposed individuals: 34 years
Clinical Presentation & Outcomes:
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Severity: All 45 patients with animal exposure had mild illness
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No hospitalizations or deaths reported
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Symptoms:
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93% (42/45) had conjunctivitis
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49% (22/45) had fever
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36% (16/45) had respiratory symptoms
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33% (15/45) had only conjunctivitis
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Duration: Median 4 days (range: 1-8 days)
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Antiviral Treatment:
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87% of patients received oseltamivir, started a median of 2 days after symptom onset
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Household Transmission:
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No additional cases among 97 household contacts
Personal Protective Equipment (PPE) Usage Among Animal Workers:
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Gloves: 71%
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Eye protection: 60%
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Face masks: 47%
Garg, S., Reinhart, K., Couture, A., Kniss, K., Davis, C.T., Kirby, M.K., Murray, E.L., Zhu, S., Kraushaar, V., Wadford, D.A. and Drehoff, C., 2025. Highly pathogenic avian influenza A (H5N1) virus infections in humans. New England Journal of Medicine, 392(9), pp.843-854.