Influenza A (H3N2)v (cont.)

Medical Author:
Medical Editor:
Medical Editor:


The above information was published in January; since then, the situation with the H3N2v virus has changedagain. In July 2012, the CDC noted a significant increase in the number of humans with H3N2v infections. The majority of patients were children or workers at state fairs or in the swine-raising industry, so most of the patients had an association with pigs. Studies have shown that many pig populations in several U.S. states are infected with the H3N2v virus. As of August 2012, to date, about 225 human infections with H3N2v have been reported (Indiana and Ohio have the highest number of H3N2v infections). The CDC suggests that the infection seems to be spreading from pigs to humans and has detected no easy transfer of the virus between humans. They do caution, however, that with the rapid genetic changes that can occur with influenza A viruses, human-to-human transmission may occur in the future, especially since the strain has acquired the M (matrix) gene from the 2009 H1N1 pandemic virus. Currently, there have been no deaths caused by this virus and only a few (eight) hospitalizations; the CDC currently thinks the clinical evidence suggests H3N2v produces illness no more severe than the seasonal flu. However, with the influenza A viruses like H3N2v, the CDC plans to keep a close watch on how the flu progresses this season.

The following are the new CDC recommendations to avoid getting H3N2v infections from pigs:

CDC Recommendations for People at High Risk

  • If you are at high risk of serious flu complications and are going to a fair where pigs will be present, avoid pigs and swine barns at the fair this year. This includes children younger than 5 years of age, people 65 years of age and older, pregnant women, and people with certain long-term health conditions (like asthma, diabetes, heart disease, weakened immune systems, and neurological or neurodevelopmental conditions).

CDC Recommendations for People Not at High Risk

  • Don't take food or drink -- or eat, drink, or put anything in your mouth -- in pig areas.
  • Don't take toys, pacifiers, cups, baby bottles, strollers, or similar items into pig areas.
  • Wash your hands often with soap and running water before and after exposure to pigs. If soap and water are not available, use an alcohol-based hand rub.
  • Avoid close contact with pigs that look or act ill.
  • Take protective measures if you must come in contact with pigs that are known or suspected to be sick. This includes wearing protective clothing, gloves, masks that cover your mouth and nose, and other personal protective equipment.
  • Watch your pig (if you have one) for signs of illness and call a veterinarian if you suspect it might be sick.
  • Avoid contact with pigs if you have flu-like symptoms. Wait seven days after your illness started or until you have been without fever for 24 hours without the use of fever-reducing medications, whichever is longer. If you must have contact with pigs while you are sick, take the protective actions listed above.

The CDC also points out that current seasonal flu vaccine will not protect individuals from H3N2v infection but does mention that antiviral drugs (listed above in the article) may be helpful in reducing or eliminating symptoms. Influenza A H3N2v may change in the future so this article topic may come around...again.


United States. Centers for Disease Control and Prevention. "Information on Influenza A (H3N2) Variant Viruses ("H3N2v")." Aug. 20, 2012. <>.

United States. Centers for Disease Control and Prevention. "More H3N2v Cases Reported, Still Linked to Pig Exposure." Aug. 17, 2012. <>.

United States. Centers for Disease Control and Prevention. "Seasonal Influenza (Flu)." Dec. 23, 2011. <>.

United States. Centers for Disease Control and Prevention. "Take Action to Prevent the Spread of Flu Between People and Pigs at Fairs." Aug. 20, 2012. <>.

United States. Centers for Disease Control and Prevention. "Update: Influenza A (H3N2)v Transmission and Guidelines - Five States, 2011." MMWR 60.51 Jan. 6, 2012: 1741-1744. <>.

Last Editorial Review: 8/22/2012