WHO: Swine Flu Now A Pandemic, 1st In 41 Years

The U.N. is keen to avoid panic. "We must guard against rash and discriminatory action, such as travel bans or trade restrictions," said U.N. Secretary-General Ban Ki-moon.

Fear has already gripped Argentina, where thousands have flooded hospitals this week, bringing emergency health services in Buenos Aires to the brink of collapse during winter weather. Last month, a bus arriving in Argentina from Chile was stoned by people who thought a passenger had swine flu.

China has quarantined travelers, including New Orleans Mayor Ray Nagin, on the slightest suspicion of contact with an infected person.

The U.S. government has already increased the availability of flu-fighting medicines and authorized $1 billion for developing a new swine flu vaccine. In addition, new cases seem to be declining in many parts of the country, U.S. health officials say, as North America moves out of its traditional winter flu season.

Still, New York City reported three more swine flu deaths Thursday, including a child under 2, a teenager and a person in their 30s.

"Countries where outbreaks appear to have peaked should prepare for a second wave of infection," Chan warned.