Swine Flu in Japan May Trigger Pandemic

In U.S., 8 New York City Schools Closed as H1N1 Swine Flu Spreads Across Nation

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May 18, 2009 -- H1N1 swine flu appears to be spreading in Japan, pushing the world to the brink of an official flu pandemic.

Japan's cases of H1N1 spiked today with 104 new lab-confirmed cases, raising that nation's swine-flu case count from 25 to 129. Ten schools in the Kobe City area reported 78 of the new cases.

If the new cases do indeed represent "community-level sustained transmission" of the virus in Asia, it would be the second region of the world to have wide spread of H1N1 swine flu. That would meet the official WHO criteria for moving from the current level 5 pandemic alert to the ultimate level 6 alert.

Aside from the emotional shock, the formal pandemic declaration won't mean a lot to the U.S., Anne Schuchat, MD, the CDC's interim deputy director for science, said at a news conference.

"We have seen sustained spread of this virus in the U.S. and are acting aggressively, so a change from level 5 to level 6 will have less effect on us than on other regions that have done less to deal with virus," she said.

Declaration of a pandemic does not mean that the virus has become more deadly, only that it is spreading more widely around the globe.

While H1N1 swine flu does appear more dangerous than seasonal flu bugs -- especially for older children, teens, and young adults -- the vast majority of cases have been relatively mild.

"From the virus strains we have tested we see no indication of a change to more virulent strain. But viruses do change and we will continue looking at this," Schuchat said.

Even so, the U.S. has recorded its sixth swine flu fatality, a 55-year-old assistant principal at a school in the New York City borough of Queens. The city has closed eight schools in Queens and Brooklyn; news reports suggest that 40 other New York schools have high absentee rates.

Despite the worrisome news from New York, Schuchat said the swine flu is now spreading most quickly in the Pacific Northwest and in the Southwest. Case counts -- 5,123 as of today -- are "the tip of the iceberg."


"The way this virus is spreading in the U.S., we are not out of the woods and disease is continuing," Schuchat said.

More than 200 Americans have been hospitalized. Most of those hospitalized have been young people between that ages of 5 and 24, and very few have been over 65. The reason for this is not clear.

That's the same disease pattern seen worldwide. In a speech today to the World Health Organization's annual meeting of health ministers, WHO Director-General Margaret Chan, MD, said that while the WHO has not yet declared a pandemic, H1N1 swine flu is expected to spread rapidly to new countries.

"The virus has given us a grace period, but we do not know how long this grace period will last. No one can say whether this is the calm before the storm," Chan said.

Chan gave voice to health experts' greatest fear: that the H1N1 swine flu might recombine with the H5N1 bird flu. Such a recombination might make the mild H1N1 more deadly -- or might give the H5N1 bird flu virus the ability to spread easily from person to person.

"We must never forget the H5N1 avian influenza virus is now firmly entrenched in poultry in several countries," Chan said. "No one can say how this avian virus will behave when pressured by large numbers of people infected with the new H1N1 virus."

Travel Restrictions to Mexico Eased

None of these dire possibilities has yet come to pass. The good news is that in Mexico, the first country to be affected by H1N1 swine flu, the epidemic seems to be waning.

"The overall trend seems downward in Mexico," Schuchat said. "We have downgraded our travel advice. Earlier, we recommended that people defer nonessential travel; now we offer a precaution to those at risk of complications of flu due to pregnancy, underlying conditions, or old age. But we do think it is fine for most people to travel to Mexico at this point."

With cases still on the rise in the U.S., it's too soon to know whether H1N1 swine flu will continue to spread throughout the summer or whether it will go away -- at least until the fall flu season.


Despite school closings in some areas, most U.S. schools will start summer vacation in the next few weeks. It's not known how that might affect the spread of the virus in communities.

"In most of the U.S. the environment changes quite a bit during the summer and the humidity might be less conducive to flu circulating," Schuchat said. "We would love to see an end to these outbreaks affecting schools, but colleagues tell me we have seen outbreaks in summer camps, and we need to be alert to that possibility."

WebMD Health News Reviewed by Louise Chang, MD on May 18, 2009



Anne Schuchat, MD, interim deputy director for science and public health program, CDC.

Margaret Chan, MD, director-general, World Health Organization.

News release, New York City Department of Health, May 17, 2009.

World Health Organization, Regional Office for the Western Pacific, news release, May 18, 2009.

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