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Content on this page was developed during the 2009-2010 H1N1 pandemic and has not been updated.

  • The H1N1 virus that caused that pandemic is now a regular human flu virus and continues to circulate seasonally worldwide.
  • The English language content on this website is being archived for historic and reference purposes only.
  • For current, updated information on seasonal flu, including information about H1N1, see the CDC Seasonal Flu website.

Human Swine Influenza Investigation

April 23, 2009
See most recent information

Human cases of swine influenza A (H1N1) virus infection have been identified in San Diego County and Imperial County, California as well as in San Antonio, Texas.

Human Cases of Swine Flu Infection
State # of laboratory
confirmed cases
California 5 cases
Texas 2 cases
Cases will be updated daily at 3 PM ET

Investigations are ongoing to determine the source of the infection and whether additional people have been infected with similar swine influenza viruses.

CDC is working closely with state and local officials in California and Texas and other health and animal officials on investigations into these cases.

Topics on this page:

General Information

Swine Flu and You
What is swine flu? Are there human infections with swine flu in the U.S.? …

Key Facts about Swine Influenza (Swine Flu)
How does swine flu spread? Can people catch swine flu from eating pork? …

Swine Influenza in Pigs and People
Brochure

Guidance

CDC has provided the following interim guidance for this investigation.

Residents of California and Texas
CDC has identified human cases of swine influenza A (H1N1) virus infection in people in these areas. CDC is working with local and state health agencies to investigate these cases. We have determined that this virus is contagious and is spreading from human to human. However, at this time, we have not determined how easily the virus spreads between people. As with any infectious disease, we are recommending precautionary measures for people residing in these areas.

  • Cover your nose and mouth with a tissue when you cough or sneeze. Throw the tissue in the trash after you use it.
  • Wash your hands often with soap and water, especially after you cough or sneeze. Alcohol-based hands cleaners are also effective.
  • Try to avoid close contact with sick people.
  • If you get sick, CDC recommends that you stay home from work or school and limit contact with others to keep from infecting them.
  • Avoid touching your eyes, nose or mouth. Germs spread that way.

There is no vaccine available at this time, so it is important for people living in these areas to take steps to prevent spreading the virus to others. If people are ill, they should attempt to stay at home and limit contact with others. Healthy residents living in these areas should take everyday preventive actions.

People who live in these areas who develop an illness with fever and respiratory symptoms, such as cough and runny nose, and possibly other symptoms, such as body aches, nausea, or vomiting or diarrhea, should contact their health care provider. Their health care provider will determine whether influenza testing is needed.

Clinicians
Clinicians should consider the possibility of swine influenza virus infections in patients presenting with febrile respiratory illness who:

  1. Live in San Diego County or Imperial County, California or San Antonio, Texas or
  2. Have traveled to San Diego and/or Imperial County, California or San Antonio, Texas or
  3. Have been in contact with ill persons from these areas in the 7 days prior to their illness onset.

If swine flu is suspected, clinicians should obtain a respiratory swab for swine influenza testing and place it in a refrigerator (not a freezer). Once collected, the clinician should contact their state or local health department to facilitate transport and timely diagnosis at a state public health laboratory.

State Public Health Laboratories
Laboratories should send all unsubtypable influenza A specimens as soon as possible to the Viral Surveillance and Diagnostic Branch of the CDC’s Influenza Division for further diagnostic testing.

Public Health /Animal Health Officials
Officials should conduct thorough case and contact investigations to determine the source of the swine influenza virus, extent of community illness and the need for timely control measures.

Interim Guidance on Infection Control and Antiviral Recommendations for Patients with Confirmed or Suspected Swine Influenza A Virus Infection, April 20, 2009
Guidance for health care workers and public health personnel…

Press

CDC Briefing on Public Health Investigation of Human Cases of Swine Influenza
April 23, 2009 press briefing…

Publications

Swine Influenza A (H1N1) Infection in Two Children – Southern California, March—April 2009
Morbidity and Mortality Weekly Report (MMWR) April 21, 2009 / Vol. 58 / Dispatch

 
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