What You Need to Know About Swine Flu


  • Swine influenza, or “swine flu”, is a highly contagious acute respiratory disease of pigs, caused by one of several swine influenza A viruses.
  • Swine influenza viruses are most commonly of the H1N1 subtype, but other subtypes are also circulating in pigs (e.g., H1N2, H3N1, H3N2)
  • The H3N2 swine virus was thought to have been originally introduced into pigs by humans.
  • Sometimes pigs can be infected with more than one virus type at a time, which can allow the genes from these viruses to mix. This can result in an influenza virus containing genes from a number of sources, called a “reassortant” virus.
  • Although swine influenza viruses are normally species specific and only infect pigs, they do sometimes cross the species barrier to cause disease in humans.
  • The 2009 Swine flu outbreak in humans is due to a new strain of influenza A virus subtype H1N1 that derives in part from human influenza, avian influenza, and two separate strains of swine influenza.

Modes of Transmission:

  • Most infections occur among people with direct pig contact.
  • Sometimes a flu virus can mutate to be more transmissible to humans.
  • People who work with swine, especially people with intense exposures, are at risk of catching swine influenza if the swine carry a strain able to infect humans.
  • Swine flu cannot be spread by pork products, since the virus is not transmitted through food

Period of Communicability:

  • The swine flu in humans is most contagious during the first five days of the illness although some people, most commonly children, can remain contagious for up to ten days.

swine flu Signs and Symptoms:

The signs and symptoms of swine flu are similar to those of influenza and of influenza-like illness in general:

  1. chills
  2. fever
  3. sore throat
  4. muscle pains
  5. severe headache
  6. coughing
  7. weakness
  8. general discomfort

Diagnostic Procedures:

  • To diagnose swine influenza A infection, a respiratory specimen would generally need to be collected within the first 4 to 5 days of illness (when an infected person is most likely to be shedding virus).
  • However, some persons, especially children, may shed virus for 10 days or longer.
  • Identification as a swine flu influenza A virus requires sending the specimen to CDC for laboratory testing.

Vaccines and Treatment:

  • Officials do not know if the seasonal flu vaccine will protect against the A(H1N1) swine flu virus.
  • In the laboratory, the antiviral drugs Tamiflu and Relenza are effective against this new flu; amantadine and rimantadine are not.

Safety precautions:

  1. Cover your nose and mouth with a tissue when coughing or sneezing.
  2. Wash hands regularly with soap and water, especially after you cough or sneeze.  Alcohol-based hand cleaners are also effective.
  3. Avoid close contact with sick people.
  4. If sick, self-monitor and stay home from work or school and limit contact with others.
  5. Consult your doctor immediately should signs and symptoms of flu persist.


Department of Health

Centers for Disease Control and Prevention

World Health Organization


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