The World Health Organization says 42 countries are reporting there
have been more than 11,000 cases of the swine influenza A-H1N1 virus.
its latest figures, the Geneva-based WHO says 86 deaths have been
reported from the virus, with most of the fatalities in Mexico, the
epicenter of the outbreak.
In other developments, U.S.
researchers say new test results show that people in their 60s and
older show signs of greater immunity to the virus.
Atlanta-based Centers for Disease Control and Prevention issued the
assessment Thursday as the number of U.S. swine flu cases climbed past
5,700. The CDC says more than 60 percent of U.S. infections have
occurred in patients younger than 25.
The CDC says one possible
explanation is that older adults were either infected with or
vaccinated against a much older strain that more closely resembles the
H1N1 virus. But the researchers say it is still not clear how safe
older people are from the new infection.
Health officials say
the current batch of seasonal flu vaccine provides virtually no
protection against the new H1N1 strain. Seasonal flu is usually more
severe in very young children, older people and those with certain
The U.S. has the greatest number of
infections, followed by Mexico with nearly 3,900. But Mexico has the
most deaths, 75, while the U.S. has had 10 fatalities.
City, the swine flu alert level Thursday was dropped to green, the
lowest level. Officials say there have been no new infections in a
week. The flu's impact is expected to cost the Mexican economy $2.2