Human infections with various subtypes of avian influenza A viruses, both low pathogenic and highly pathogenic, have been reported sporadically worldwide. These infections can lead to a wide range of disease severity, such as conjunctivitis, mild upper respiratory tract illness, pneumonia, respiratory and multiorgan failure, and even death. Pathogenicity in infected poultry does not necessarily translate to the same disease severity in infected humans.
Commercial influenza tests in clinical settings can identify influenza A viruses in respiratory specimens but cannot differentiate between seasonal influenza A viruses and influenza A viruses of animal origin. If H5 is suspected, test by CDC H5 primer/probe set; send presumptive positive specimens to CDC for testing.If recent swine exposure and H1 or H3 is positive, and subtyping is presumptive positive for a variant influenza A virus, send specimens to CDC for testing.If influenza A positive on a commercial influenza test, collect respiratory specimens for influenza A virus subtyping at a public health laboratory.
Oseltamivir is recommended for patients who are hospitalized or outpatients with progressive or severe disease. The CDC recommends standard oseltamivir dosing for outpatients and longer treatment for severe disease; however, the optimal duration is unknown. While there have been no clinical trials, observational studies have reported that starting oseltamivir treatment soon after illness onset is associated with greater survival vs later initiation of antiviral treatment.