(PTI): Amid the rise in global health alerts, American authorities warn that the swine flu outbreak has hit 11 US states and closed schools in eight.

Following WHO’s alert that declared a Phase 5 outbreak, US officials have announced that swine flu has sickened nearly 100 in 11 states.

Eight states closed 100 schools on Wednesday and more might need to be shut down temporarily. The schools’ closing affected 53,000 students in Texas alone. The schools have been closed to keep crowds from forming, thought to be one way to slow down the spread of the flu.

Mexico, the first country to report swine flu, has already closed schools nationwide until at least May 6.

The virus, a mix of pig, bird and human genes to which people only have a limited natural immunity, has spread to at least nine countries.

President Barack Obama pledged “great vigilance” in confronting the swine flu outbreak as it claimed the life of one person in the United States.

A Mexican toddler who visited Texas with his family was confirmed to be the first sufferer to have died in the country.

No vaccine has been developed to fight the virus named H1N1; the symptoms have been treated with antivirals. It is feared, however, that H1N1 might resist antiviral medications.