May 4, 2009


Early Calculations Show Swine Flu Hard to Transmit (Michael Fumento, 5/04/09,

It SEEMS like swine flu isn't particularly infectious by looking at case numbers and consulting news stories that continue to find a strong link to Mexico. But there's a scientific way of measuring using what's called a "basic reproductive number."

That essentially means the measure of how many secondary cases a typical patient will cause in a population with no immunity to the pathogen. Keep in mind that as an epidemic progresses, the number drops because the pathogen finds fewer and fewer susceptible victims. That's why all epidemics can be roughly plotted on the shape of a bell curve. (When I wrote that about U.S. AIDS epidemic, I was called a fruitcake. AIDS subsequently followed the shape of a bell curve.)

The director of Mexico's National Center for Epidemiology and Disease Control, told the Washington Post "According to the preliminary models, the reproductive number that we have in the Mexico City metropolitan area is 1.5," noting, "It's a fairly low number, and that's good news."

Indeed for SARS, which caused only 8096 cases and 774 deaths over a period of about 170 days (115 cases and 4.5 deaths per day), the figure was 3.0.

For other contagious diseases, according to the CDC, it's vastly higher: 6-7 for diphtheria, 12-18 for measles, 4-7 for mumps, and 6-7 for Rubella.

Most importantly for our purposes the basic reproductive number for seasonal flu seems to range from 1.5 to 3.0. (Although you do see much higher numbers.)

That means no swine flu pandemic.

Mexico says flu epidemic over the worst (Louise Egan and Luis Rojas Mena, 5/03/09, Reuters)
Mexico announced on Sunday its swine flu epidemic had passed the worst and experts said the new H1N1 virus might be no more severe than normal flu, although it could still have an impact on world health.

Health Minister Jose Angel Cordova showed journalists a graph indicating infections in Mexico, the epicenter of the H1N1 flu outbreak, had fallen sharply from a peak on April 24.

"The admittance of patients to hospitals has decreased and the health of patients in hospitals has improved," he told a news conference.

Posted by Orrin Judd at May 4, 2009 11:57 AM
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