Highly Pathogenic Avian Influenza A(H5N1) Virus Infections in Humans.

Summary

Among 46 U.S. human H5N1 infections, illness was predominantly mild and ocular (93% conjunctivitis), with no hospitalizations or deaths and no detected transmission to 97 household contacts. Despite prompt antiviral use, PPE use was suboptimal, underscoring the need for strengthened occupational protections (especially eye protection) in exposed workers.

Key Findings

• Among 46 cases, 20 had poultry exposure, 25 had dairy cow exposure, and 1 had no identified exposure.
• Illness was predominantly mild: 93% conjunctivitis, 49% fever, 36% respiratory symptoms; no hospitalizations or deaths.
• No secondary cases were detected among 97 household contacts.
• Most patients (87%) received oseltamivir within a median of 2 days of symptom onset.
• PPE use among exposed workers was suboptimal: gloves 71%, eye protection 60%, masks 47%.

Clinical Implications

Clinicians should screen exposed workers for ocular symptoms, consider early antivirals, and reinforce PPE including eye protection. Public health should address PPE access, training, and surveillance to detect non-respiratory presentations.

Limitations

• Descriptive surveillance with relatively small sample size limits precision
• Potential ascertainment bias and limited follow-up for delayed complications

Future Directions

Evaluate determinants of ocular-predominant disease, optimize PPE strategies (especially eye protection) in agricultural settings, and continue genomic/epidemiologic surveillance for changes in transmissibility or severity.