How do people get infected with bird flu viruses, including H7N9 virus?
Human infections with bird flu viruses are rare, but have happened in the past, usually after close contact with infected birds (both live and dead) or exposure to environments contaminated with bird flu virus, such as visiting a live poultry market.
Infected birds can shed a lot of bird flu viruses, for example, in their droppings or their mucus. If someone touches an infected bird or an environment contaminated with virus and then touches their eyes, nose or mouth, they may be infected with bird flu virus. There is some evidence that infection may also occur if the flu virus becomes aerosolized in contaminated material, such as when an infected bird flaps its wings. If someone were to breathe in airborne virus, it's possible they could get infected.
Poultry infected with H7N9 virus do not experience any illness signs or symptoms. H7N9 virus-infected poultry are well-appearing, but transmission to humans can occur. H7N9 virus has been found in birds (poultry) and contaminated environments in China in some of the same areas where human infections have happened. Available evidence suggests that most people have been infected with H7H9 virus after having contact with infected poultry or contaminated environments, including visiting a live poultry market.
Is infection with this virus serious?
Most of the reported human cases H7N9 virus infection have had very serious illness, including severe pneumonia, and about 40% of reported human cases have resulted in death. However, there also are a small number of reports of milder human illness and one possible report of a person who tested positive for H7N9 virus who did not have any symptoms.
What are the signs and symptoms of illness with H7N9 virus infection?
Signs and symptoms of H7N9 virus infection in people have started with high fever and cough. A lot of the cases have progressed to very serious illness, including severe pneumonia, acute respiratory distress syndrome (ARDS), septic shock and multi-organ failure leading to death.