Human infection with avian influenza viruses
The risk from avian influenza is generally low to most people because the viruses occur mainly among birds and do not usually
infect humans. However, more than 100 human cases of avian influenza infection have been reported since 1997. Most cases of
avian influenza infection in humans have resulted from contact with infected poultry (e.g., domesticated chicken, ducks, and
turkeys) or surfaces contaminated with secretion/excretions from infected birds. The spread of avian influenza viruses from
one ill person to another has been reported very rarely, and transmission has not been observed to continue beyond one person.
There are many different subtypes of type A influenza viruses. These subtypes differ because of changes in certain proteins
on the surface of the influenza A virus (hemagglutinin [HA] and neuraminidase [NA] proteins). There are 16 known HA subtypes
and 9 known NA subtypes of influenza A viruses. Many different combinations of HA and NA proteins are possible. Each combination
represents a different subtype All known subtypes of influenza A viruses can be found in birds.
Usually, “avian influenza virus” refers to influenza A viruses found chiefly in birds, but infections with
these viruses can occur in humans. “Human influenza virus” usually refers to those subtypes that spread widely
among humans. There are only three known A subtypes of influenza viruses (H1N1, H1N2, and H3N2) currently circulating among
humans. It is likely that some genetic parts of current human influenza A viruses came from birds originally. Influenza A
viruses are constantly changing, and they might adapt over time to infect and spread among humans.
During
an outbreak of avian influenza among poultry, there is a possible risk to people who have contact with infected birds or surfaces
that have been contaminated with secretions or excretions from infected birds.
Symptoms of avian influenza in humans have ranged from typical human influenza-like symptoms (e.g., fever, cough, sore
throat, and muscle aches) to eye infections, pneumonia, severe respiratory diseases (such as acute respiratory distress),
and other severe and life-threatening complications. The symptoms of avian influenza may depend on which virus caused the
infection.
Studies done in laboratories suggest that the prescription medicines approved in the United States for human influenza
viruses should work in treating avian influenza infection in humans. However, influenza viruses can become resistant to these
drugs, so these medications may not always work. Additional studies are needed to demonstrate the effectiveness of these medicines.
From: CDC Website
