"The vast majority of all human cases and deaths from H5N1 have occurred in previously healthy children and young adults. Experience in Asian countries and most recently in Turkey underscores the fact that immediate clear public information is critical to help protect human health," he said.
Dr David Nabarro, the United Nations bird flu chief, warned that the arrival of the virus in Nigeria increased the prospect of it spreading worldwide, because several migratory routes intersect in that country. He added: "If it turns out that H5N1 was carried to west Africa by migratory birds, we need to be prepared for the possibility that within the next six months it could be brought back to the northern hemisphere - but perhaps along a different flight route."
"And that could mean that countries in Western Europe and North America should be bracing themselves for the possible introduction of H5N1 avian influenza," he said.
Lake Chad, a major stopping off point for migratory wildfowl, may have been the entry point for the virus in west Africa. Officially, Nigerian bureaucrats have formally confirmed the presence of H5N1 on just four farms in the north of the country. But media reports suggest that large numbers of birds have died on scores of farms across at least four states, and that the outbreak has been spreading for the past month.
Health ministry officials confirmed that they were testing two children who fell ill after contact with diseased birds last week. If those tests are positive, they would be the first human victims of the deadly virus in Africa. Against World Health Organisation advice, trade in live birds continued in northern cities, although sellers in Kano complained to reporters of falling trade.
Mohammed Belhoecine, the Nigeria representative of the WHO, said: "This is an emergency situation and it is very important to stop the handling, trading and movement of birds."
Dr Jong-wook said the home slaughter and consumption of birds, which appear to be sick, was a high-risk behaviour. "There is a risk that outbreaks of H5N1 infections in birds could spread within Nigeria and into neighbouring countries. Nigeria is one of several African countries located on the Black Sea- Mediterranean fly way used by migratory birds," he said.
He added that human and animal health services must be on high alert sharing information and quickly reporting any signs of disease in birds or human that could be due to H5N1 avian influenza. Dr Jong-wook said African health systems were already struggling to cope with children and adults suffering from HIV/AIDS, tuberculosis, malaria, respiratory infections and other infectious conditions.
Dr Jong-wook said human cases of H5N1 may be difficult to distinguish from other illnesses."We simply do not know what the impact of exposure to avian influenza will be on many who may be already immunocompromised and in a fragile state of health. Health workers must be fully alert and samples must be taken and sent to laboratories. When human cases of H5N1 are identified, co-ordinated human and animal health investigations will be essential," he stated.
He went on to say that there was no time to waste and the WHO was ready to help all African countries take measures to reduce the risks of H5N1. And according to the budget estimates in this year's yellow book, the Zambian government under the Ministry of Health has a proposed allocation of K20 million towards prevention of H5N1 avian influenza.
Bird flu has killed at least 88 people and infected 165 since it re-emerged in late 2003. Most of the victims are in East Asia. In Indonesia, two women in their 20s had tested positive for the virus and were being treated at a specialist Jakarta hospital, while the WHO confirmed an 11th case in China.