Nigerian agriculture officials said the virus was detected in samples taken on Jan. 16 from birds on a large commercial poultry farm located in the Kaduna state in northern Nigeria. Other mysterious poultry deaths in neighboring Kano and Plateau states have not been confirmed as the bird flu.
The outbreak marks the first reported occurrences of the H5N1 strain in Africa, the world's poorest continent that officials fear is ill-equipped to deal with a new major health crisis.
There are no reported human cases in Africa, though authorities say it is difficult to rule out because people are often buried without a formal medical check due to high mortality rates.
"The prospect of bird flu loose in sub-Saharan Africa is a scary one because of the way that human and domestic bird populations are so closely intermingled," said associate professor Phil Hockey of the Percy FitzPatrick Institute of African Ornithology in Cape Town.
Investigations are under way to determine if the virus has spread to household flocks in Africa where most people live in close contact with birds and maintain free-ranging poultry flocks. Most of the human cases reported to the World Health Organization had close contact with diseased or dead poultry but experts are concerned that the disease could mutate into a form that could be easily transmittable from human to human and spark a global pandemic.
The bird flu has killed 88 people of 165 confirmed cases in Asia, Turkey and Iraq. On Thursday, the Chinese government announced another human case bringing the total cases in China to 11 since the disease's appearance in late 2003.
Health officials stress that a quick response to contain the virus' spread among birds is the best way to reduce human infections. Nigeria has killed around 46,000 chicken, geese and ostriches and has said it will quarantine or cull all livestock in any farm suspected of having bird flu. In war-ravaged Iraq, which recently reported its first human case, police are struggling to control the disease and are urging residents to kill their birds.
"Fighting the avian influenza in animals is the most effective and cost-effective way to reduce the likelihood of H5N1 mutating or reassorting to cause a human flu pandemic," said U.N. Food and Agriculture Organization Deputy Director-General David Harcharik. "Avian influenza should not only be considered as a human health issue, but as a human and animal health issue."
The WHO plans to compare data from the Nigerian outbreak with other viruses that have caused human cases to assess the risk to human health.
The FAO has not identified the source of the Nigerian outbreak but suspects birds spread the disease along migration routes from central Asia. In January after the virus reached Turkey at the crossroads of Asia, Europe and Africa, officials at the FAO warned that countries along spring migratory routes in Africa should be extremely vigilant.