Influenza A Variant Viruses (H3N2v, H1N1v, H1N2v)

Influenza viruses that normally circulate in pigs are called "variant" viruses when they are found in people. In 2011, a small number of humans was found to be infected with an influenza A H3N2v virus in the United States. Since 2011, sporadic cases cases of H3N2v, H1N1v, and H1N2v have been reported anually in the United States. A majority of these cases has occured during summer months, associated with contact with swine at fair environments.

One case of variant influenza has been identified in North Dakota. The North Dakota Department of Health put out the following news release: North Dakota Department of Health Reports First Variant Influenza Case. Because infection with H3N2v can be mild in some people, it is possible people have been infected but not tested, or were tested in a clinical setting without further investigation. Testing for variant influenza can only be done through state health departments and the CDC. In a doctor's office or hospital, someone with variant influenza will most likely test positive for seasonal influenza, but may also test negative all together. It is important to keep this in mind when veiwing statistics for variant influenza.

On July 31, 2014 it was reported that three pigs at the 2014 North Dakota State Fair had been removed for illness and had tested positive for an H3N2 virus. The North Dakota Department of Agriculture put out the following news release: Precautions advised regarding influenza. No cases of human infection related to contact with these animals or their environs at the State Fair have been discovered. The North Dakota Department of Health asks that anyone who becomes sick with influenza-like illness (fever, sore throat, coughing, etc.) after coming in contact with swine or swine environments, such as pig barns, should mention the exposure to their doctor if they seek medical treatment.

Medical providers should contact the North Dakota Department of Health, Division of Disease Control when patients are being evaluated for variant influenza. Possible variant influenza is considered novel influenza, and is immediately notifiable via telephone. In addition, providers should be aware commercial influnza test kits, including commercial molecular methodologies, such as PCR, used at large hospitals, are not always reliable at detecting variant influenza. A commercial laboratory negative for seasonal influenza SHOULD NOT be used to rule out novel influenza.

Prevention Information

This section provides information and links to resources that can be used to help prevent the spread of H3N2v influenza.

Reduce and prevent the spread of influenza between people by practicing the following:

  • Cover your nose and mouth when coughing or sneezing
  • Wash your hands
  • Do not touch your eyes, nose or mouth
  • Stay home if you are sick

Reduce and prevent the spread of influenza between people and pigs by practicing the following:

  • Don't eat, drink, or put items in your mouth in areas with pigs
  • Don't take toys, pacifiers, cups, baby bottles, strollers, or similar items into areas with pigs
  • Wash your hands before and after contact with pigs
  • Avoid close contact with pigs that appear ill
  • Avoid contact with pigs if you are sick with influenza or influenza-like illness

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, people 65 years and older, pregnant women, and people with certain long-term health conditions (such as asthma, diabetes, heart disease, weakened immune systems, and neurological or neurodevelopmental conditions).

CDC Guidance

The links below provide background information, guidance documents, and other resources for healthcare professionals, schools and other partners to use regarding variant influenza.

Prevention Information for the Public (CDC)

Healthcare Providers and Laboratories ((CDC)

Fair Guidance (CDC)