Los Angeles County public health officials today reported no confirmed cases of swine flu locally but said they were closely monitoring hospitals and schools for signs of the influenza strain. The Centers for Disease Control and Prevention confirmed 20 cases of the virus nationwide, including seven in California and eight in New York City, according to the CDC’s website. All seven California cases have been in San Diego and Imperial counties. The flu has led to numerous deaths in Mexico. Dr. Robert Kim-Farley, L.A. County’s director of communicable disease control and prevention, said that none of the cases in the United States was fatal but that local public health officials "feel that this new strain is of serious concern." He added that it would not be "unexpected to see cases occurring in Los Angeles." Kim-Farley said county health officials had put their operations center on 24-hour watch to detect the virus and were keeping a close eye on schools and hospitals. He said a public health laboratory also had been activated to receive additional specimens from people suspected of having contracted the virus. He said cases in the United States so far can "be characterized as mild" and that two prescription medications, Tamiflu and Relenza, seemed to be effective in combating the flu strain. An outbreak of swine flu in Mexico may have contributed to the deaths of as many as 86 people and sickened many others. Authorities there have closed schools and ordered other emergency health measures to contain the virus. Cases also have been confirmed in Canada and are suspected in New Zealand, France, Spain and Israel. Federal officials declared a public health emergency because of the virus. "That sounds more severe than really it is," Janet Napolitano, the U.S. Homeland Security secretary, said at a news conference today, according to a transcript of the briefing. "This is standard operating procedure and allows us to free up federal, state and local agencies and their resources for prevention and mitigation; it allows us to use medication and diagnostic tests that we might not otherwise be able to use, particularly on very young children; and it release funds for the acquisition of additional antivirals." In San Diego, where the first cases of swine flu in the U.S. were reported last week, health officials reported no new cases Sunday, although they warned that more could be found as investigations continue. Four cases have been diagnosed in San Diego County, and three people have been diagnosed in the Imperial Valley. Dr. Wilma Wooten, public health officer for San Diego County, continued to warn residents to take seriously any signs of flu and to stay away from work and seek medical care if they are sick. Physicians have been asked to report flu cases to county health officials. U.S. Customs and Border Protection agents at the San Diego and Imperial County border crossings have been alerted to look for persons crossing into the U.S. who appear to have flu symptoms. Those persons are then sent to a secondary screening process. In secondary processing, people can be given instructions on finding medical care and, in extreme cases, denied entry. Agents also have access to masks and gloves both for themselves and for members of the public. The agency is also in contact with the Centers for Disease Control and Prevention. So far, no one crossing into the U.S. from Mexico has appeared to have the symptoms of swine flu, officials said. Jack O’Connell, state superintendent of public instruction, also said today that the public can download posters titled "Keep Our School Healthy" and "Germ-Free Zone" with tips on how to avoid the flu. They are available in English, Spanish, Vietnamese and other languages. Kim-Farley of the Los Angeles County Department of Public Health said those with mild illnesses should be staying home. Anyone with flu-like symptoms — such as a fever, cough or sore throat — who has recently traveled to Mexico should see a doctor. In a statement posted on the L.A. County department’s website, agency director Dr. Jonathan E. Fielding said: "We do not suggest any changes in what you would normally do to avoid either getting sick yourself or passing illness to others: if you are sick, stay home; if your child is sick, do not send him or her to school; cover your mouth when you cough or sneeze; wash your hands frequently, especially before eating and after using the restroom; and do not touch your eyes, nose or mouth with your hands." -- Ari B. Bloomekatz and Tony Perry

