The first quick-and-dirty analysis of Mexico's swine flu outbreak suggests that the H1N1 virus is about as dangerous as the virus behind a 1957 pandemic that killed 2 million people worldwide. But it's not nearly as lethal as the bug that caused the 1918 Spanish flu pandemic.
The world first became aware of this latest outbreak of swine flu in late April (click here for full swine flu timeline). Researchers recognized that the new virus was also causing disease in Mexico. As of today, there have been more than 5000 confirmed cases worldwide and fewer than 50 confirmed deaths.
In an effort to understand how the virus spread, an international team led by epidemiologist and disease modeler Neil Ferguson of Imperial College London closely examined the Mexican outbreak with the most current data available. The researchers calculated that each infected person transmitted the virus to about 1 1/2 other people and that it had been around long enough to copy and spread between groups of people between 14 to 73 times.
The team also showed a strong link between air travel out of Mexico and confirmed cases in other countries. The case fatality rate—the percentage of infected people who died—was estimated to be 0.4%, with a range between 0.3% and 1.5%. That's far less than the devastating pandemic of 1918 but still substantial, the team reports online today in Science.
Epidemiologist Arnold Monto, a flu specialist at the University of Michigan School of Public Health in Ann Arbor, praises the speedy collaboration among researchers from the United Kingdom, Mexico, and the World Health Organization to produce the study. He notes that in other outbreaks, many heavily affected countries have hesitated to share data.
Yet Monto cautions that the findings are provisional and that the wide ranges in the estimates indicate limited confidence in the conclusions. "They have been dealing with what they have to work with in terms of the data," says Monto.
Epidemiologist Lone Simonsen of George Washington University in Washington, D.C., also notes that the number of confirmed cases in Mexico is probably a vast underestimate, as the sickest cases are most likely to be tested for the virus. As more mild cases are detected, the denominator could rise, which would lower the fatality rate. "It's quite possible that the confirmed cases are the tip of the iceberg," she says. "The uncertainty in the denominator means they could be two or three orders of magnitude off."
Still, both Simonsen and Monto say that they welcome fast-and-dirty analyses right now. "We need to very speedily learn about the infections in the first affected countries," says Simonsen. "We have burning questions to answer."
—Jon Cohen
In Mexico it is well known the action that the goverment takes when a bad things happen. They hide it all. Itis possible that the Mexican goverment its holding important information to the international community for its own good; elections comming in July and the now ruling party its attacked for its conections with druglords, are making this flu outbreack into a good election bonus. Even when around the world we are seeing more cases here in Mexico the sanitary measures are decreasing ad the only news coming in the air on TV and radio are that the goverment has now contained the outbreack. Schools are not receiving any chlorine or alcohol, and students are not beeing watched. Also there have been many cases when infected people have been sent home with no antiviral drugs, one of this cases was confirmed to be a AH1N1 virus. International organisms should watch closesly in Mexico beacuse the goverment its just making a show of sanitary measures and not taking any real action.
A Mexican