Avian Influenza is a contagious viral infection that can affect domestic poultry and wild birds. The main subtype, the potent flu virus known as H5N1 was discovered in 1997, when it first infected humans during a poultry outbreak in Hong Kong SAR, China.
Today, the main cause is contact with infected birds, which can shed the virus in their saliva, nasal secretions and feces.
Most avian influenza viruses do not cause disease in humans. But some – including the subtype known as H5N1 currently circulating in parts of Asia and northeast Africa – have caused human disease and deaths since 1997. Transmission to humans has occurred through close contact with infected birds or contaminated environments.
Avian influenza viruses do not pose a food safety risk as long as poultry products are properly handled and cooked.
An outbreak confirmed December 2 in in B.C.’s Fraser Valley involves a highly-pathogenic H5N2 virus. A highly-pathogenic virus causes severe illness and death in birds, particularly poultry, while a low-pathogenic virus causes less severe illness and lower rates of mortality.
Migratory birds such as geese are known carriers of Avian Influenza and transmission tends to occur along north-south flyways. The virus might be carried to a domestic poultry operation by a person, a vehicle, feed, equipment, birds or animals.
“There are a hundred different ways it could get in, even with good bio-security in place,” says Dr. Andrew Potter, professor of veterinary microbiology with the Western College of Veterinary Medicine at the University of Saskatchewan and director and CEO of the Vaccine and Infectious Disease Organization.
Avian Influenza outbreaks are not confined to large-scale, commercial operations – some incidents of H5N1 in Asia, for example, took place in what could be considered mom-and-pop operations – but large industrial operations allow for rapid spread.
“Obviously, if you have a large number of animals in a small area, you’re going to multiply the effects, fairly rapidly,” Dr. Potter says.
So far, the Fraser Valley outbreak involved 8 sites, according to the most recent updates, and 155,000 birds that were already dead or to be killed.
In 2004, an outbreak of avian influenza H7N3 swept through the Fraser Valley and resulted in the cull of about 17 million birds.