Investigation and Interim Recommendations: Swine Influenza (H1N1) CDC, in collaboration with public health officials in California and Texas,

Investigation and Interim Recommendations: Swine Influenza (H1N1) CDC, in collaboration with public health officials in California and Texas,is investigating cases of febrile respiratory illness caused by swine influenza (H1N1) viruses. As of 11 AM (EDT) April 25, 2009, 8 laboratory confirmed cases of Swine Influenza infection have been confirmed in the United States. Four cases have been reported in San Diego County, California. Two cases have been reported in Imperial County California. Two cases have been reported in Guadalupe County, Texas. Of the 8 persons with available data, illness onsets occurred March 28-April 14, 2009. Age range was 7-54 y.o. Cases are 63% male. The viruses contain a unique combination of gene segments that have not been reported previously among swine or human influenza viruses in the U.S. or elsewhere. At this time, CDC recommends the use of oseltamivir or zanamivir for the treatment of infection with swine influenza viruses. The H1N1 viruses are resistant to amantadine and rimantadine but not to oseltamivir or zanamivir. It is not anticipated that the seasonal influenza vaccine will provide protection against the swine flu H1N1 viruses. CDC has also been working closely with public health officials in Mexico, Canada and the World Health Organization (WHO). Mexican public health authorities have reported increased levels of respiratory disease, including reports of severe pneumonia cases and deaths, in recent weeks. CDC is assisting public health authorities in Mexico by testing specimens and providing epidemiological support. As of 11:00 AM (EDT) April 25, 2009, 7 specimens from Mexico at CDC have tested positive for the same strain of swine influenza A (H1N1) as identified in U.S. cases. However, no clear data are available to assess the link between the increased disease reports in Mexico and the confirmation of swine influenza in a small number of specimens. WHO is monitoring international cases. Further information on international cases may be found at: http://www.who.int/csr/don/2009_04_24/en/index.html Clinicians should consider swine influenza infection in the differential diagnosis of patients with febrile respiratory illness and who 1) live in San Diego or Imperial counties, California, or Guadalupe County, Texas, or traveled to these counties or 2) who traveled recently to Mexico or were in contact with persons who had febrile respiratory illness and were in one of the three U.S. counties or Mexico during the 7 days preceding their illness onset. Patients who meet these criteria should be tested for influenza, and specimens positive for influenza should be sent to public health laboratories for further characterization. Clinicians who suspect swine influenza virus infections in humans should obtain a nasopharyngeal swab from the patient, place the swab in a viral transport medium, refrigerate the specimen, and then contact their state or local health department to facilitate transport and timely diagnosis at a state public health laboratory. CDC requests that state public health laboratories promptly send all influenza A specimens that cannot be subtyped to the CDC, Influenza Division, Virus Surveillance and Diagnostics Branch Laboratory. Persons with febrile respiratory illness should stay home from work or school to avoid spreading infections (including influenza and other respiratory illnesses) to others in their communities. In addition, frequent hand washing can lessen the spread of respiratory illness. CDC has not recommended that people avoid travel to affected areas at this time. Recommendations found at http://wwwn.cdc.gov/travel/contentSwineFluUS.aspx will help travelers reduce risk of infection and stay healthy. Clinical guidance on laboratory safety, case definitions, infection control and information for the public are available at:http://www.cdc.gov/swineflu/investigation.htm. • Swine Influenza A (H1N1) Virus Biosafety Guidelines for Laboratory Workers: http://www.cdc.gov/swineflu/guidelines_labworkers.htm • Interim Guidance for Infection Control for Care of Patients with Confirmed or Suspected Swine Influenza A (H1N1) Virus Infection in a Healthcare Setting: http://www.cdc.gov/swineflu/guidelines_infection_control.htm • Interim Guidance on Case Definitions for Swine Influenza A (H1N1) Human Case Investigations: http://www.cdc.gov/swineflu/casedef_swineflu.htm Morbidity and Mortality Weekly Reports Dispatch (April 24) provide detailed information about the initial cases at http://www.cdc.gov/mmwr/preview/mmwrhtml/mm58d0424a1.htm For more information about swine flu: http://www.cdc.gov/swineflu