Almost all cases of H5N1 virus infection in people have been associated with close contact with infected live or dead birds, or H5N1-contaminated environments, for example live bird markets. There have been some instances of spread from infected mammals to humans as well. While there may have been some cases that were not detected, the virus does not seem to easily infect humans or spread from person to person, based on the current knowledge and understanding.

Influenza patients should be managed properly to prevent severe illness and death. Patients with laboratory-confirmed influenza virus infection with progressive, complicated or severe illness – or those with asymptomatic or mild disease but who are at increased risk of severe disease – should be treated with antiviral medicines, for example oseltamivir, as soon as possible.

The symptoms of H5N1 infection may include fever (often high fever, > 38°C) and malaise, cough, sore throat and muscle aches. Other early symptoms may include conjunctivitis and other non-respiratory symptoms. The infection may progress quickly to severe respiratory illness and neurologic changes (altered mental status or seizures). · H5N1 virus has also been detected in samples collected from people without symptoms who had exposure to infected animals or their environments.