Avian influenza viruses generally do not infect humans. However, some highly pathogenic strains of avian influenza have historically been responsible for cases of human infection and death.
Avian influenza became a human health concern in 1997 when an epidemic of highly pathogenic H5N1 avian influenza in Hong Kong infected eighteen people and killed six. In nearly all those cases, the infection occurred after close contact with diseased poultry, infected bird products such as feathers and manure, or contaminated surfaces such as dirt, water, or cages. To this day, less than 500 people have died from highly pathogenic H5N1. By comparison, 33,000 to 36,000 people in the United States die each year from seasonal human influenza. Although the number of people historically infected with highly pathogenic H5N1 is relatively few, 60 percent of those infected die, causing concern among public health officials.
Even if the highly pathogenic H5N1 strain is found in the United States, it would not be an immediate human health concern because the virus has not yet gained the capability to readily transmit from human to human. If the virus mutates into a strain that can easily be transmitted from human to human, it could trigger the start of a pandemic and potentially result in significant loss of human life.
There is currently no human vaccine commercially available for preventing the highly pathogenic H5N1 avian influenza. The drug oseltamivir has been found to have some benefits for those who are already sick. Some cases of resistance to the drug have already been reported.
Humans often play a key role in the spread of the disease. Improper handling and processing of birds, some of which may be infected with avian influenza, in backyard flocks and live bird markets contribute to the spread of the disease. Additionally, those who smuggle infected poultry, poultry products, or wild birds for the pet industry may spread avian influenza to previously unaffected countries. The virus can also be spread inadvertently by the legal trade and transportation of infected poultry, eggs, and poultry products.