Bird flu (avian influenza)
While we sniffle our way through winter, we are not alone. Birds can also be affected by various strains of bird ‘flu. The avian influenza (AI) virus generally causes mild disease in birds, but there are some strains of the virus that are very powerful and cause death. Such strains are called ‘highly pathogenic avian influenza’ (HPAI) or ‘fowl plague’.
Recently in some parts of Asia, one of these powerful stains, called H5N1, devastated chicken and other poultry flocks. This outbreak has hit countries such as Thailand and Vietnam hardest, as they rely on chickens for food and export. Thailand is the fourth largest chicken exporter in the world.
Other countries such as Cambodia, Indonesia, Japan, China, South Korea and the Philippines have also reported cases of H5N1 virus infection; some countries such as Japan and South Korea have been able to control these outbreaks quickly and safely. Avian influenza has also reached Europe and the United Kingdom, although no human cases of the infection have been reported.
The new strain is also causing concern because it has infected some people who have had close contact with sick birds, and has led to numerous human deaths in Thailand and Vietnam.
Whilst these people were infected directly from birds, there is a fear that the virus could mutate to gain the ability to transmit from one person to another as easily as a normal ‘flu virus. If the virus also adapts to humans, it could lead to a global pandemic that could kill millions of people.
The World Health Organization (WHO) is also concerned as the H5N1 strain has been detected in migratory geese, which means that the disease could be spread when the birds travel during change of seasons; they predict that India could be at greatest risk from these birds.
The WHO is also encouraging changes to farming practices and marketing of live animals to reduce the risk of the H5N1 strain to humans.
There is currently no vaccine against the H5N1 strain to protect people or birds and because a pandemic strain of influenza could appear at any time, the WHO maintains a worldwide surveillance of ’flu strains and makes predictions of suitable strains for vaccine production. An experimental vaccine that stimulates the body to fight off the H5N1 virus appears to be effective, but a major problem remains - in the event of a flu pandemic, there would be a shortage of the vaccine as the vaccine is grown in chicken eggs and production can take months.
Human ’flu can be detected in the doctor’s surgery using a test that detects antibodies to the influenza virus, but does not identify the specific strain. For this, a DNA-based test is needed.
Currently any researchers working with the H5N1 virus wear a special suit (a biocontainment suit) to prevent infection and they work in a laboratory which is certified as a biocontainment laboratory and has strict controls against infection.
For news about avian influenza go to:
Poultry news: http://www.thepoultrysite.com
New Scientist: http://www.newscientist.com/channel/health/bird-flu
The World Health Organization: http://www.who.int/csr/disease/avian_influenza/en/