UN health agency chief puts Southern Hemisphere on alert for A(H1N1) virus

A swab test for A(H1N1) virus in Mexico City, Mexico

22 May 2009 – Health authorities around the world need to be vigilant as the influenza A(H1N1) virus meets seasonal flu viruses flowing through the yet unaffected Southern Hemisphere, warned the head of the United Nations World Health Organization (WHO) today.

“The current winter season gives influenza viruses an opportunity to inter-mingle and possibly exchange their genetic material in unpredictable ways,” WHO Director-General Margaret Chan said in her closing remarks to the World Health Assembly in Geneva.

One month after the outbreak of the new flu strain, WHO expects it to continue spreading to new countries and within nations already affected over the coming weeks, said Dr. Chan.

According to WHO, as of this morning, some 42 countries had reported 11,168 laboratory confirmed cases of the infection, including 86 deaths.

However, Dr. Chan noted that the pandemic alert level remains at Phase 5 – on a six-point warning scale – meaning that sustained human-to-human transmission of the virus on a community level is mostly restricted to a single geographic region, in this case North America.

During the high-level consultation on pandemic influenza, several delegations called on WHO to consider criteria other than geographical spread when evaluating the phases of influenza pandemic alert.

Dr. Chan stressed that up to now, the new virus has largely circulated in the Northern Hemisphere, where epidemics of seasonal influenza should be winding down.

“We need to watch the behaviour of A(H1N1) very carefully as it encounters other influenza viruses circulating during the winter season in the Southern Hemisphere,” she said. “The current winter season gives influenza viruses an opportunity to inter-mingle and possibly exchange their genetic material in unpredictable ways.”

Although WHO does not predict a dramatic jump of severe or fatal infections, Dr. Chan warned that countries where the virus is already widespread should expect to see more cases of this type of infection.

“But countries, especially in the developing world, where populations are most vulnerable, should prepare to see more than the present small number of severe cases, which are being picked up under the best detection and testing conditions possible.”

The week-long session of the World Health Assembly, which gathered officials from the 193 WHO member countries, wrapped up today with the adoption of 15 resolutions on a variety of global health issues, including primary health care, the prevention and control of multidrug-resistant and extensively drug-resistant tuberculosis, public health, innovation and intellectual property and pandemic influenza preparedness.

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