A RECENT analysis of human cases of the highly pathogenic avian influenza A(H5N1) virus in the USA has provided new insights into the virus’s effects.
Between March–October 2024, 46 individuals were confirmed to have contracted the virus. The Centers for Disease Control and Prevention (CDC) influenza A/H5 subtyping kit was employed to confirm the presence of the A(H5N1) virus in patient samples. Most cases were linked to exposure to infected animals, primarily poultry and dairy cows.
Twenty patients had direct contact with infected poultry, while 25 were exposed to dairy cows. One case was detected through routine surveillance, with no identifiable exposure to infected animals. This patient experienced non-respiratory symptoms and was hospitalised, but did not face severe complications.
The majority of the 45 patients with known animal exposure were adults with a median age of 34 years. All of these individuals experienced mild symptoms, with the most common being conjunctivitis (93%), followed by fever (49%) and respiratory issues (36%). Notably, 33% of patients only had conjunctivitis, and the illness generally lasted between 1–8 days, with a median duration of 4 days.
The patients were treated with the antiviral drug oseltamivir, which was typically administered 2 days after symptom onset. Fortunately, no deaths or hospitalisations occurred, and no additional cases were reported among 97 household contacts of infected individuals. This suggests that there was no evidence of human-to-human transmission of the virus.
Despite the relatively mild outcomes, the use of personal protective equipment among workers exposed to infected animals was suboptimal, with only 71% using gloves and 60% wearing eye protection. The findings reinforce the need for improved safety measures to reduce the risk of exposure in occupational settings.
Ada Enesco, EMJ
Reference
Garg S et al. Highly pathogenic avian influenza A(H5N1) virus infections in humans. N Engl J Med. 2024;DOI:10.1056/NEJMoa2414610.
