Also known as bird flu, it is an infectious disease in birds caused by several strains of the influenza virus. It was identified in Italy in 1878. All bird species are at risk, although some are more liable to infection than others.
The natural host for the virus is migratory waterfowl, such as wild ducks, which have a high resistance to infection. Domestic poultry are particularly susceptible.
The disease can be spread via bird droppings (which contaminate dust and soil) and farm equipment such as vehicles or clothing. The trade in live birds between countries has also caused the virus to spread.
What Happens To Birds That Get It?
The symptoms vary widely, from none or mild illness to highly contagious and rapidly fatal epidemics. The contagious form has sudden onset, severe illness, and carries a death rate of nearly 100 percent. The virus can alter from being low-risk to high-risk very quickly through genetic mutation.
Where Is The Disease Found?
The H5N1 strain of avian flu has been found in Thailand, Vietnam, Indonesia, Cambodia, China, Hong Kong, Japan, the Philippines, Mongolia, Malaysia, and North Korea. More recently it has spread to Russia and Kazakhstan. In 2003, there was an outbreak of the highly pathogenic H7N7 strain in the Netherlands and Germany.
How Many Birds Are Affected?
In the latest outbreak, which started in late 2003, more than 150 million birds have been killed or culled in Southeast Asia alone. The total number affected is expected to be much higher.
What Is The Danger To Humans?
Avian flu currently poses only a small danger, as the virus does not normally infect animals other than birds or pigs. However, human beings have been infected in Vietnam, Thailand, Cambodia, and Indonesia, although these cases were linked to direct contact with dead or diseased poultry. One case of human-human contact was suspected in Thailand in 2004. There is no vaccine to prevent H5N1 infection in human beings, although there are drugs to treat the illness.
Why Are Scientists Worried?
When H5N1 has infected human beings it is exceptionally lethal -- of 112 confirmed cases, 57 have died. The concern is that this strain will mutate so that it can be easily passed on from one person to another -- if this happens, the result could be a pandemic as serious as the 1918-19 “Spanish flu” that killed between 20 million and 40 million people.
Source: World Health Organization