U.S. health officials are testing for suspected cases of swine influenza, following a serious outbreak of the disease in Mexico. Swine flu is suspected of killing 149 people in Mexico and making more than 1,600 others ill. Forty cases have been confirmed in the United States. Seven of them are in California, where the state's governor, Arnold Schwarzenegger, says health workers are seeking to prevent a wider outbreak.

California Governor Arnold Schwarzenegger speaks at press conference on swine flu situation in Beverly Hills, 27 Apr 2009

Governor Arnold Schwarzenegger says swine flu struck Mexico swiftly and severely.

"That's why we here in California, we're taking quick actions here to protect everyone from this outbreak," he said. "I can assure you that, at this time, there is no reason for alarm. But we want to go and do everything that we can to make sure that we prevent an outbreak here."

US cases mild to moderate

He says all of the U.S. cases so far have been mild or moderate. He adds that influenza experts have been deployed to southern California, where seven cases of swine flu have been confirmed in San Diego and Imperial counties, near the U.S.-Mexico border.

Schwarzenegger says a dozen suspected cases are being investigated, including one further north near the state capital - Sacramento.

"And we are continuing to communicate with public health officials in Mexico," the governor said. "And we are testing patients with flu-like illnesses statewide. And we have activated our health alert network to be in touch with all the hospitals and doctors and medical centers and so on. The bottom line is, we are prepared."

Doctor says avoid crowds

U.S. officials are urging Americans to avoid non-essential travel to Mexico.  

Dr. Mark Horton, Director of California's Department of Public Health, says good hygiene, such as covering one's mouth when coughing or sneezing, can also minimize the spread of the disease.

"Hand-washing is still one of the most important things we can do," said Horton. "But certainly avoiding crowded conditions, if you're in an area where the influenza has shown up already are other steps that we can take. It's important for the public to be involved in this."

U.S. officials are sending California more than one million treatment courses of anti-viral drugs, including Tamiflu, to be used in the event of a wider swine flu outbreak.