Influenza (Flu) in Arizona

H3N2v – Variant Viruses

Influenza A (H3N2) Variant Viruses ("H3N2v") in the U.S.

Influenza is a common respiratory disease among humans, and influenza activity increases every year in the U.S., usually in the winter months. Influenza viruses are also common among other animals, including pigs and birds, and can cause similar symptoms in these animals. While the influenza viruses that cause illness in pigs or birds (called "swine influenza viruses" or "avian influenza viruses") do not usually affect humans, every so often swine or avian influenza viruses can cause illness in people. When this happens, the viruses are called "variant viruses". In the past, a human case of an influenza virus that normally spread in pigs was detected every one to two years in the U.S.

More recently, there has been an increase in the number of human variant virus cases detected in the U.S. In 2011, 12 human cases of a particular virus normally seen in pigs were identified, called influenza A (H3N2) variant, or H3N2v. Since July, 2012, many more human cases of this illness have been detected.

See the CDC website for more information about these viruses.

Current U.S. Numbers

No cases of this illness have been identified in Arizona. Testing currently conducted at the Arizona State Public Health Laboratory can detect presumptive positive cases.

CDC publishes the number of identified cases in the U.S. on their website each Friday.

Risk Factors

Most human cases of H3N2v are in people with exposure to infected pigs (e.g. children near pigs at a fair or workers in the swine industry). The virus is thought to spread when an infected pig coughs or sneezes and droplets with influenza virus in them spread through the air. If these droplets land in your nose or mouth, or are inhaled, you can be infected. There also is some evidence that you might get infected by touching something that has virus on it and then touching your own mouth or nose. Eating properly handled and prepared pork (pig meat) or other products made from pigs has not been shown to cause swine influenza.


To reduce the spread of influenza viruses, including H3N2v, CDC recommends you take everyday preventive actions, including:

  • 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. If soap and water are not available, an alcohol-based hand rub may be used.
  • Avoid touching your eyes, nose or mouth. Germs spread that way.
  • Try to avoid close contact with sick people.
  • If you are sick, stay home from work or school until your illness is over.

To prevent the spread of flu viruses between people and pigs, CDC recommends:

  • Wash your hands frequently with soap and running water before and after exposure to animals.
  • Never eat, drink or put things in your mouth in animal areas.
  • Children younger than 5 years, people 65 years and older, pregnant women, and people with certain chronic medical conditions (like asthma, diabetes, heart disease, weakened immune systems, and neurological or neurodevelopmental conditions) are at high risk from serious complications if they get influenza. These people should consider avoiding exposure to pigs and swine barns this summer, especially if sick pigs have been identified.
  • If you have animals—including swine—watch them for signs of illness and call a veterinarian if you suspect they might be sick.
  • Avoid close contact with animals that look or act ill, when possible.
  • Avoid contact with pigs if you are experiencing flu-like symptoms.

If you must come in contact with pigs while you are sick, or if you must come in contact with pigs known or suspected to be infected, or their environment, you should use appropriate protective measures (for example, wear protective clothing, gloves, masks that cover your mouth and nose, and other personal protective equipment) and practice good respiratory and hand hygiene.

For more information, read the CDC factsheet on H3N2v.

For those who work with swine at fairs, it's important to follow good hygiene, for your health and the health of your animals. Learn more on the Department of Agriculture website.

Guidance and Recommendations

CDC has posted guidance on several topics for controlling the spread of H3N2v viruses. Topics include:

  • Protecting yourself against H3N2v
  • Controlling the spread of flu at fairs
  • Prevention strategies for healthcare settings
  • Information for clinicians
  • Guidance for school administrators

Visit the CDC website for these resources and more.

Clinicians who believe they may have a patient with H3N2v infection should contact their local health department.