Three years after swine flu closed Mexico City and caused an international scare, the Mexican government and local media are at odds over the severity of this season's flu virus.

A new strain of the swine flu virus called A(H3N2) may now be spreading through person-to-person contact, the Public Health Agency of Canada says.

After a lull of several months, an influenza virus that is sporadically jumping from pigs to people in the United States has made another appearance.

More people may have been infected by the virus that causes bird flu than previously thought, and the number of deaths from H5N1 infection may have been "overestimated," according to a study in the journal Science.