Besser confirmed that the virus found in Americans is the same as that in Mexicans, but that they have not been able to determine why the impact of the flu has been more severe in Mexico, where about 86 people have died from the disease. In the U.S., only one person infected had to be hospitalized. Officials stressed they are taking an aggressive approach to tackling the issue -- they have released 12.5 million of the nation's stockpile of 50 million courses of Tamiflu, a drug that has shown itself at least initially to be effective against the flu virus -- but used cautious language in descrbing whether it could be contained.
"Even if this outbreak is a small one we can't anticipate we wont have follow up outbreaks," said U.S. Homeland Security Secretary Janet Napolitano.
In Mexico, more than a thousand people have been infected. The Mexican government has advised people to stay homebound, and the government has indicated those infected could be isolated. In the country's deserted capital, public events were cancelled for the next week or so. Sales of masks have soared as people try to prevent themselves from the potentially deadly disease.
"If we move the pandemic threat, want to make sure on pretty good solid ground. Such a move would be a big signal to the world. We already have several countries involved (with positive cases), but we know in current global situation that cases can occur in many places without ever taking hold. We have decided to wait and get more information," said Dr Keiji Fukuda, assistant director-general ad. interim for Health Security and Environment at WHO.
WHO officials said so far, the virus has only been confirmed in Mexico and the United States, and that the transmissability is limited and the outbreak is small. WHO officials said are working on a vaccine and testing and identifying this particular never-seen-before virus.
The severity of the flu is still unknown. Some U.S. doctors say they do not trust information from Mexico, but WHO officials said they do not believe that Mexico created any delays in reporting the outbreak.
"We only have isolated reports from various places. You have to have more than this" to declare a pandemic, said Peter Katona, an associate professor at the University of California, Los Angeles (UCLA) Medical Center. "This virus may burn itself out tomorrow. We don't know that yet."
Several countries have reportedly announced measures to test American visitors and imposed travel warnings for Mexico. The United States has not yet imposed a travel advisory to and from Mexico, with officials only suggesting to Americans to reevaluate their plans if visiting the country.
American Airlines, US Airways and Continental are waiving fees for flight changes to Mexico. They are not cancelling flights, and American Airlines said it's only received a handful of calls seeking changes in travel plans.