California's top health officials are saying the state expects
to find more cases of the new strain of flu that has killed up to
60 people in Mexico and infected eight in the United States,
calling the outbreak still "largely a mystery."
California, home to six of the US cases, said it was coordinating with federal and international officials in what Gov Arnold Schwarzenegger called a "rigorous and thorough" response to the still-unfolding health crisis.
"When you start looking more intensely you are likely to find more cases," said Dr Gil Chavez, director of the Center for Infectious Diseases at the California Department of Public Health and the state's chief epidemiologist.
"There's evidence of possible human-to-human transmission going on, so the more we look the more we are likely to find," Chavez told Reuters in an interview.
Chavez said the state was studying the profiles of the cases so far found and ramping up testing of hospitalised patients in an effort to understand the outbreak.
"We are watching this very closely. Its largely a mystery. Its very unusual whenever you have as many as even six cases (of swine flu), that's very, very rare," Chavez said.
"To have that happen in six unrelated instances in California and have none of those individuals having come in contact with each other is very unusual so we are very much trying to stay on top of it," he said.
Chavez said that because symptoms of the new strain of swine flu so closely resemble more common respiratory flu strains, it was likely other cases had not been detected.
Health officials were advising Californians to take precautions and had alerted hospitals across the state to use "extreme infection control" measures.
Chavez said even stronger steps, including monitoring those crossing the border or even quarantines, could be considered depending on the extent or severity of the outbreak.
"This is something we believe we identified early and have responded to very aggressively and we are taking every step necessary to solve the mystery," he said.
Schwarzenegger said California had requested extra flu experts from the US Centers for Disease Control and was expanding lab testing and testing and monitoring of animals. The state has activated its Joint Emergency Operations Center and been in communication with officials in Mexico.
The governor advised Californians to take "common-sense" steps to avoid contracting the flu, including covering the nose and mouth when sneezing, washing hands often with soap and water and avoiding close contact with others.
Four of Mexico's suspected cases have been reported in Mexicali, which shares a border with California.