This is an official
CDC Health Advisory
Distributed via Health Alert Network
April 25, 2009, 3:00 EST (03:00 PM EDT)
CDCHAN-000281-2009-04-25-ALT-N
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
Additional information is also available by calling 1-800-CDC-INFO
(1-800-232-4636)