US Homeland Security chief Janet Napolitano declared a health emergency as the Centers for Disease Control confirmed at least 20 cases of swine flu in five states, including eight high school students in the New York borough of Queens.

The US government said the afflicted were carrying the same strain of virus that had by Monday killed over 100 people in Mexico.

“We expect to see more cases of swine flu. As we continue to look for cases, I expect we’re going to find them,” said Richard Besser, acting director of the Centers for Disease Control, the New York Times reported.

The Spanish Health Ministry confirmed a case of swine flu and that 17 more sick people were being investigated, on April 27.