Swine Flu Pandemic Over, WHO Declares

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But H1N1 Flu Bug Still Here, Becoming Seasonal Virus

By Daniel J. DeNoon
WebMD Health News

Reviewed By Laura J. Martin, MD

Aug. 10, 2010 -- The H1N1 swine flu pandemic is over, the World Health Organization declared today.

The world has now entered the "post-pandemic period" in which the H1N1 virus has begun acting like -- and circulating with -- other flu bugs.

"The new H1N1 virus has largely run its course," WHO Director-General Margaret Chan, MD, said at a news teleconference. Her decision follows the advice of the WHO's Emergency Committee, which met this morning.

In the U.S., the pandemic emergency declaration expired June 23. But before officially ending the pandemic, the WHO waited to see what the winter flu season would look like in the Southern Hemisphere and whether there would be unusual summer swine flu outbreaks in the Northern Hemisphere.

That wait is over. The WHO ended the pandemic because:

• H1N1 has spread to all countries.
• Many people in all age groups have some immunity to the H1N1, either via infection or vaccination.
• There were no unusual summer outbreaks of H1N1.
• H1N1 swine flu is no longer the dominant flu virus, crowding out others. Seasonal flu bugs -- H3N2 type A and type B viruses -- are being reported.

According to the CDC, the WHO declaration will change nothing except the ending of weekly reports to international health agencies. The U.S. already is going ahead with plans to treat the H1N1 swine flu virus as part of future flu seasons.

H1N1 Swine Flu Still Here

The end of the pandemic does not mean that H1N1 swine flu has gone away. It's likely that the virus still poses a risk to pregnant women and infants. It's not yet clear whether older children and young adults will continue to be at highest risk of severe H1N1 disease.

And because flu can be a serious disease, the WHO and the CDC recommend getting the seasonal flu vaccine. The vaccine for the 2010-2011 season includes the H1N1 swine flu virus, as well as the type A H3N2 and type B viruses.

Children aged 6 months to 8 years who have not been vaccinated against H1N1 will need two doses of the new seasonal vaccine, given at least four weeks apart.

H1N1 Swine Flu: Bullet Dodged?

Compared to the doomsday scenario of a highly lethal mutant flu bug, the H1N1 swine flu pandemic was mild.

"This time around, we have been aided by pure good luck," Chan said. "This pandemic has turned out to be much more fortunate than what we feared a little over a year ago."

Chan said the pandemic wasn't as bad as feared because:

• The 2009 H1N1 virus did not mutate to a more lethal form. In fact, it changed surprisingly little. Vaccines made against virus isolated early in the pandemic remained effective throughout the pandemic.
• Although the swine flu bug showed some signs of becoming resistant to the antiviral drug Tamiflu, widespread resistance never developed.
• The vaccine was effective and remarkably safe.

"Had things gone wrong in any of these areas, we would be in a very different situation today," Chan said.

SOURCES: WHO web site.

CDC, email communication.

CDC, Recommendations for the Prevention and Control of Influenza with Vaccines, July 29, 2010.

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