Saturday, April 25, 2009

Swine Flu Epidemic

Swine Flu Epidemic

Probably the most well known is an outbreak of swine flu among soldiers in Fort Dix, New Jersey in 1976. The virus caused disease with x-ray evidence of pneumonia in at least 4 soldiers and 1 death; all of these patients had previously been healthy. The virus was transmitted to close contacts in a basic training environment, with limited transmission outside the basic training group. The virus is thought to have circulated for a month and disappeared. The source of the virus, the exact time of its introduction into Fort Dix, and factors limiting its spread and duration are unknown. The Fort Dix outbreak may have been caused by introduction of an animal virus into a stressed human population in close contact in crowded facilities during the winter. The swine influenza A virus collected from a Fort Dix soldier was named A/New Jersey/76 (Hsw1N1).

Sixty people in Mexico have died of the flu -- and so far, 16 of the deaths are confirmed cases of swine flu, news sources quote Mexican officials as saying.

World Health Organization spokesman Gregory Hartl told the Canadian news agency CBC that there have been some 800 cases in Mexico City, where schools are closed due to the outbreak.

Alarmingly, the flu outbreak in Mexico is striking healthy young people -- a pattern that would be expected if a flu virus new to humans emerged.

"Because these cases are not happening in the very old or the very young, which happens with seasonal influenza, this is an unusual event and a cause for heightened concern," Hartl said in a CBC interview.

That's not the only eyebrow-raising feature of the swine flu outbreaks. Infections have occurred in Mexico, California, and Texas -- where warm weather should mean the end of the normal flu season, says William Schaffner, MD, president-elect of the National Foundation for Infectious Diseases and chair of preventive medicine and infectious diseases at Vanderbilt University.

"Will we see this flu virus transmitted in the warm months? That would give us heatburn," Schaffner tells WebMD. "And is this a harbinger of things to come during our next flu season?"

Another disconcerting feature of the outbreak is that it's probably too late to contain it to limited geographical areas.

"We are seeing cases in Texas and California with no connection between them. This makes us think there has been transmission from person to person through many cycles," Besser said. "For containment we need limitation to a confined geographical area, and we have not seen that here."

The World Health Organization is convening an expert panel to determine whether to raise its pandemic flu alert level. Because of Bird FLU, we're at level 3. If the panel finds evidence of "increased human-to-human transmission" it goes to level 4. If there's evidence of "significant human-to-human transmission," it goes to level 5.

A pandemic will be declared only if there is "efficient and sustained human-to-human transmission" of a new flu virus. That clearly has not happened yet.


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