Infection

The causative agent is the avian influenza (AI) virus. AI viruses all belong to the influenza virus A genus of the Orthomyxoviridae family and are negative-stranded, segmented RNA viruses.

Avian influenza spreads in the air and in manure. Wild fowl often act as resistant carriers, spreading it to more susceptible domestic stocks. It can also be transmitted by contaminated feed, water, equipment and clothing; however, there is no evidence that the virus can survive in well cooked meat.

The incubation period is 3 to 5 days. Symptoms in animals vary, but virulent strains can cause death within several days.

Avian Influenza in Humans

While avian influenza spreads rapidly among birds, it does not infect humans easily, and there is no confirmed evidence of human-to-human transmission. Of the 15 subtypes known, only subtypes H5 and H7 are known to be capable of crossing the species barrier.

The symptoms of avian influenza in humans are akin to those of human influenza, ie. fever, sore throat, cough and in severe cases pneumonia. Human deaths from avian influenza were unknown until 1997, when six people in Hong Kong died from the particularly virulent H5N1 strain.

In January 2004, a major new outbreak of H5N1 avian influenza surfaced again in Vietnam and Thailand's poultry industry, and within weeks spread to ten countries and regions in Asia, including Indonesia, South Korea, Japan and China. Intensive efforts were undertaken to slaughter chickens, ducks and geese to contain the outbreak. Nevertheless, the human death toll has so far reached 20 people, in Vietnam and Thailand.

It is feared that if the avian influenza virus undergoes antigenic shift with a human influenza virus, the new subtype created could be both highly contagious and highly lethal in humans. Such a subtype could cause a global influenza pandemic, similar to the Spanish Flu that killed over 20 million people in 1918. In February 2004, avian influenza virus was detected in pigs in Vietnam, increasing fears of the emergence of new variant strains.

Prevention and Treatment

Avian influenza in humans can be detected reliably with standard influenza tests. Antiviral drugs are clinically effective in both preventing and treating the disease. Vaccines, however, take at least four months to produce and must be prepared for each subtype.

External link

• WHO Avian Influenza Fact Sheet