Avian influenza (also known as bird flu) is a type of influenza virulent in birds. It was first identified in Italy in the early 1900s and is now known to exist worldwide.

Contents

1 Infection 2 Avian influenza in humans 3 Prevention and treatment 4 Increasing virulence 5 Symptoms 6 External link

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.

Cats are also thought to be possible infection vectors for H5N1 strains of avian flu.

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

Avian influenza in humans

Of the 15 subtypes known, only subtypes H5 and H7 are known to be capable of crossing the species barrier from birds to humans. 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 (though a variety of sources quote average figures even higher, up to 40 million in some cases).

The first cases of avian influenza passed from birds to human was H5N1 in 1997 in Hong Kong. 16 people were infected, with 4 people died. The outbreak was limited in Hong Kong, without spreading to any other places. All chickens in the territory were slaughtered.

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 mainland China. Intensive efforts were undertaken to slaughter chickens, ducks and geese (over 40 million chickens alone were slaughtered in high-infection areas), and the outbreak was contained by March, but the total human death toll in Vietnam and Thailand was 23 people. In February 2004, avian influenza virus was detected in pigs in Vietnam, increasing fears of the emergence of new variant strains.

Fresh outbreaks in poultry were confirmed in Ayutthaya and Pathumthani provinces of Thailand, and Chaohu city in Anhui, China, in July 2004.

In North America, the presence of avian influenza was confirmed at several poultry farms in British Columbia in February 2004. As of April 2004, 18 farms have been quarantined to halt the spread of the virus. Two cases of humans with avian influenza have been confirmed in that region.

In August 2004 Avian Flu was confirmed in Kampung Pasir, Kelantan, Malaysia. Two chickens were confirmed to be carrying H5N1. As a result Singapore has imposed a ban on the importation of chickens and poultry products. Similarly the EU has slapped a ban on Malaysian poultry products. A cull of all poultry has been ordered by the government within a 10KM radius of the location of this outbreak.

On September 25th 2004, the World Health Organization began to suspect human to human transmission of the avian influenza virus, however, this has not yet been confirmed by a laboratory test. However, recent observation and documentation has recorded at least one case of human to human transmission of a rare strain of the influenza virus. The case was unusual, though, in that the original carrier, who received the disease from a bird, was held by her mother for roughly 5 days as the young girl died. Shortly afterwards, the mother became ill and perished as well.

An outbreak of avian influenza in January 2005 affected 33 out of 64 cities and provinces in Vietnam, leading to the forced killing of nearly 1.2 million poultry. The 2005 outbreak caused 13 deaths in Vietnam and 1 death in Cambodia.

Prevention and treatment

Avian influenza in humans can be detected reliably with standard influenza tests. Antiviral drugs are sometimes effective in both preventing and treating the disease, but no virus has ever been really cured in medical history. Vaccines, however, take at least four months to produce and must be prepared for each subtype.

Increasing virulence

In July 2004 researchers, headed by H. Deng of the Harbin Veterinary Research Institute, Harbin, China and Professor Robert Webster of the St Jude Children's Research Hospital, Memphis, Tennessee, reported results of experiments in which mice had been exposed to 21 isolates of confirmed H5N1 strains obtained from ducks in China between 1999 and 2002. They found "a clear temporal pattern of progressively increasing pathogenicity". [1] (http://www.pnas.org/cgi/content/abstract/0403212101v1)

Symptoms

In humans, it has been found that avian flu causes similar symptoms to other types of flu:

• fever
• cough
• sore throat
• muscle aches
• conjunctivitis
• in severe cases of avian flu, it can cause severe breathing problems and pneumonia, and can be fatal.

Taken from: http://www.bupa.co.uk/health_information/html/health_news/270104avianflu.html

External link

• WHO Avian Influenza Fact Sheet (http://www.who.int/csr/don/2004_01_15/en/print.html)
• WHO Avian influenza frequently asked questions (http://www.who.int/csr/disease/avian_influenza/avian_faqs/en)
• Using GIDEON to diagnose Avian Flu (http://www.gideononline.com/case/avianflu.htm)

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