Swine Flu in Japan May Trigger Pandemic
In U.S., 8 New York City Schools Closed as H1N1 Swine Flu Spreads Across Nation
"The virus has given us a grace period, but we do not know how long this grace period will last. No one can say whether this is the calm before the storm," Chan said.
Chan gave voice to health experts' greatest fear: that the H1N1 swine flu might recombine with the H5N1 bird flu. Such a recombination might make the mild H1N1 more deadly -- or might give the H5N1 bird flu virus the ability to spread easily from person to person.
"We must never forget the H5N1 avian influenza virus is now firmly entrenched in poultry in several countries," Chan said. "No one can say how this avian virus will behave when pressured by large numbers of people infected with the new H1N1 virus."
Travel Restrictions to Mexico Eased
None of these dire possibilities has yet come to pass. The good news is that in Mexico, the first country to be affected by H1N1 swine flu, the epidemic seems to be waning.
"The overall trend seems downward in Mexico," Schuchat said. "We have downgraded our travel advice. Earlier, we recommended that people defer nonessential travel; now we offer a precaution to those at risk of complications of flu due to pregnancy, underlying conditions, or old age. But we do think it is fine for most people to travel to Mexico at this point."
With cases still on the rise in the U.S., it's too soon to know whether H1N1 swine flu will continue to spread throughout the summer or whether it will go away -- at least until the fall flu season.
Despite school closings in some areas, most U.S. schools will start summer vacation in the next few weeks. It's not known how that might affect the spread of the virus in communities.
"In most of the U.S. the environment changes quite a bit during the summer and the humidity might be less conducive to flu circulating," Schuchat said. "We would love to see an end to these outbreaks affecting schools, but colleagues tell me we have seen outbreaks in summer camps, and we need to be alert to that possibility."