Virus It Self May Have Changed

By Apr. 28, 64 confirmed cases had been reported in the United States. The first cases came from San Diego County and Imperial County in California and Guadalupe County in Texas. Reports from other states rapidly followed.

 Reports of confirmed or suspected disease have also come from Canada, New Zealand, and Spain. Because some cases may be mild, there are undoubtedly more infections than have been reported.

It is not currently clear why deaths are reported in Mexico, while early reports from other countries appear to show a milder disease. One explanation is that Mexico might have a larger number of infected people.

Even if only a fraction of a percent of infected people die, that would translate into a larger number of deaths if high numbers of people were infected.

An alternate explanation is that Mexico may be more alert to the possibility of swine influenza in seriously ill people and therefore be better at detecting severe disease.

Finally, the virus itself may have changed, although this is less likely given information showing that the Mexican and U.S. strains appear to be identical in early tests.