Dr. Margaret Chan told reporters that the world is no longer in Phase 6 of influenza pandemic alert. "We are now moving into the post-pandemic period," she said. "The new H1N1 virus has largely run its course."
The WHO Emergency Committee, convened today by teleconference, determined that the pandemic no longer exists.
The world is now moving into a situation where the new virus has spread to all countries, when many people in all age groups in many countries have some immunity, where no large and unusual summer outbreaks have occurred in either Northern or Southern Hemispheres, and where seasonal influenza A (H3N2) and influenza B viruses are being reported in many countries.
Based on this overall picture, said the committee, the evidence is strong that the recent influenza pandemic patterns are transitioning towards seasonal patterns of influenza.
World Health Organization Director-General Margaret Chan (Photo courtesy WHO)
This does not mean that the H1N1 virus has gone away, Dr. Chan emphasized. "Based on experience with past pandemics, we expect the H1N1 virus to take on the behavior of a seasonal influenza virus and continue to circulate for some years to come," she warned.
The recent outbreaks of H1N1 in New Zealand and India are an example of how this flu can still infect people although the danger of a pandemic has passed.
"In fact," said Dr. Chan, "the actions of health authorities in New Zealand, and also in India, in terms of vigilance, quick detection and treatment, and recommended vaccination, provide a model of how other countries may need to respond in the immediate post-pandemic period."
The new form of influenza first appeared in April 2009 in Mexico and the southwest United States. The majority of the H1N1 cases have occurred in otherwise healthy young adults rather than in the very young and the very old, who are usually infected by seasonal influenza.
As of August 1, worldwide more than 214 countries and overseas territories or communities have reported laboratory confirmed cases of pandemic influenza H1N1 2009, and at least 18,449 people have died of the disease.
The reported number of fatal cases is an under-representation of the actual numbers as many deaths are never tested or recognized as influenza related, according to the World Health Organization.
Dr. Chan said today that globally, the levels and patterns of H1N1 transmission now being seen differ from what was observed during the pandemic and out-of-season outbreaks are no longer being reported.
"During the pandemic, the H1N1 virus crowded out other influenza viruses to become the dominant virus. This is no longer the case," she said. "Many countries are reporting a mix of influenza viruses, again as is typically seen during seasonal epidemics."
Residents of Osaka, Japan on their way to work wearing flu prevention masks, May 21, 2009. (Photo by Autumn Fiery Star)
Dr. Chan cited recently published studies indicating that 20–40 percent of populations in some areas have been infected by the H1N1 virus and so have developed some level of protective immunity.
Many countries report good vaccination coverage, especially in high-risk groups, and this coverage further increases community-wide immunity.
"Based on available evidence and experience from past pandemics, it is likely that the virus will continue to cause serious disease in younger age groups, at least in the immediate post-pandemic period," Dr. Chan said.
In addition, a small proportion of people infected during the pandemic, including young and healthy people, developed a severe form of primary viral pneumonia that is not typically seen during seasonal epidemics and is especially difficult and demanding to treat. It is not known whether this pattern will change during the post-pandemic period, further emphasizing the need for vigilance.
"Pandemics are unpredictable and prone to deliver surprises," the director-general said. "No two pandemics are ever alike. This pandemic has turned out to be much more fortunate than what we feared a little over a year ago."
"This time around, we have been aided by pure good luck," she said. "The virus did not mutate during the pandemic to a more lethal form. Widespread resistance to oseltamivir did not develop. The vaccine proved to be a good match with circulating viruses and showed an excellent safety profile."
Dr. Chan credited the international community for its "extensive preparedness and support," which allowed even countries with weak health systems to detect cases and report them promptly.
Copyright Environment News Service (ENS) 2010. All rights reserved.