Public health officials in several countries are alarmed by the outbreaks of the highly pathogenic avian influenza in poultry in Asia and are concerned that the situation could, if not tackled now, lead to an epidemic in humans. The first outbreak of the avian influenza A (H5N1) strain was confirmed in the Republic of Korea on 12 December 2003. As of 25 February 2004, there were also confirmed reports in Cambodia, China, Indonesia, Japan, Lao People's Democratic Republic, Thailand and Viet Nam. Hong Kong has also reported finding the virus in a dead peregrine. The outbreak is historically unprecedented in its scale, geographical spread and economic consequences for the agricultural sector. The presence of H5N1 in humans was confirmed in laboratory results received on 11 January from samples taken from two children and one adult with severe respiratory illness, who were admitted to the hospital in Hanoi. As of 27 February, the number of laboratory-confirmed cases in Viet Nam was 23, of which 15 were fatal. In Thailand, 7 of 10 confirmed cases were fatal. No cases were reported in China.
The Food and Agriculture Organization of the United Nations (FAO) on 30 January said that the success of eradicating avian influenza in the affected countries depends heavily on mass culling. "We are, however, concerned that mass cullings are not taking place at a speed we consider absolutely necessary to contain the H5N1 virus in the region. Compensation is often a limiting factor. As long as small farmers and commercial producers, especially in poorer countries, do not receive an adequate financial incentive for killing their chickens, they will probably not apply suggested emergency measures", said Hans Wagner, FAO senior animal production and health officer. Poorer countries, in particular, need international financial assistance and advice to address the problem. As of 25 February, an estimated 100 million birds had died or been culled during the campaign against the avian flu.
At an emergency meeting of experts on 3 and 4 February, recommendations to control the further spread of the epidemic were issued, including a targeted vaccination campaign for poultry in heavily-affected countries, to avoid mass culling outside the infected areas and damaging the livelihoods of rural households and national economies. "Culling infected flocks remains the recommended response when the disease is detected. Vaccination, when used with other control measures, such as market and movement management and good agricultural practices, offers a suitable means to support the suppression of the further spread of the virus", said Joseph Domenech, Chief of the FAO Animal Health Service.
The experts agreed that targeted vaccination would reduce the amount of virus present in the environment and the potential of avian influenza spreading to humans. The recommendations include the need for substantial international financial support to fund the control measures required, including personal protective equipment and the creation of country-specific guidelines and regional coordination programmes.
According to the World Health Organization (WHO), every case of transmission of an avian influenza virus to humans is a cause for heightened vigilance and surveillance, since influenza viruses are highly unstable and the co-circulation of highly pathogenic animal viruses with those of human could create opportunities for different species-specific viruses to exchange genetic material, creating a new influenza virus to which humans would have little, if any, immunity.
Laboratory studies have shown that isolates from this virus have a high pathogenicity and can cause severe disease in humans. Birds that survive the infection excrete virus for at least ten days, thus facilitating further spread by migratory birds and at live poultry markets, thereby increasing the opportunities for direct infection of humans.
If more people become infected, over time, the likelihood increases that they, if concurrently infected with human and avian influenza strains, could serve as the "mixing vessel" for the emergence of a novel subtype with sufficient human genes to be easily transmitted from person to person. And this would mark the start of an influenza pandemic. The successful containment of public health risks depends on WHO, its Global Influenza Surveillance Network and other international agencies, as well as the epidemiological and laboratory capacity of affected countries and the adequacy of their surveillance systems.
What is Avian Influenza?
Avian influenza or "bird flu" is an infectious disease of birds caused by type A strains of the influenza virus (H5N1). Infection causes a wide range of symptoms, from mild illness to a highly contagious and rapidly fatal disease resulting in severe epidemics, which is known as "highly pathogenic avian influenza" and is characterized by sudden onset, severe illness and rapid death, with a mortality rate that can reach 100 per cent. Avian influenza viruses do not normally infect species other than birds and pigs. The virus is of particular concern as it mutates rapidly and has a documented propensity to acquire genes from viruses infecting other animal species.
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