Swine flu

It first appeared in Mexico in March. Popularly called swine flu, the H1N1 virus turns out to have a strange mixture of viral genes; 48% of its genes are from swine flu viruses, 34% are from avian flu viruses, and 17% are from human flu viruses. A key feature of the H1N1 virus is that it can be transmitted from human to human. By yesterday, swine flu had infected nearly 2,400 people, mostly in Mexico and the United States, killing 44. Where it came from, how far it will spread, and whether it will cause a pandemic remain unanswered questions. The World Health Organization’s influenza pandemic alert is currently at phase 5, just below a phase 6 full-alert.

There have been plenty of reports in the popular press about swine flu, some true, some not. For example, initial reports of a very high death rate from swine flu had to be revised downward once it was determined that many of the deaths attributed to swine flu were not caused by H1N1. Still, a death rate of nearly 2 % in healthy adults is quite high for any flu virus. Two percent of the world’s population is how many million people???

For authoritative updates about swine flu, try the news section of a magazine such as Science (see this week’s report) or the website of the World Health Organization.