Influenza Basics
Influenza (flu) viruses have circulated in humans and animals (birds, pigs, cats, dogs, horses, etc.) for centuries. Some will infect only one type of animal. Others have more ability to move between species but may cause different signs of illness in different animals.

These viruses are very adaptive, they are able to mix with other influenza viruses and create new viruses changing how well they spread and their ability to cause disease.

Influenza Type A
One strain of influenza virus is called Influenza A. It contains genetic materials that it has picked up from influenza viruses infecting birds, pigs and people. It circulates in susceptible pig herds and can cause high fever, lethargy and respiratory symptoms (coughing and sneezing). Most influenza A viruses in pigs are different from influenza A viruses that infect people. Most of the time, these pig influenza viruses stay in pigs and these people influenza viruses stay in people. Occasionally, influenza viruses can spread from people to pigs and from pigs to people.

Nomenclature Challenges
Sometimes people get confused about what they should call influenza viruses in people and in pigs. To ensure accurate naming, the World Health Organization (WHO), in collaboration with several federal and international health organizations, announced a standardized naming convention. Influenza viruses that normally circulate in pigs and may infect humans will be referred to as “variant influenza viruses,” designated by a “v.” “Variant” designates the virus as one that varies from infecting only the species that is its usual host.

Proper H3N2 Virus Naming
U.S. Centers for Disease Control (CDC) officials say that when influenza A (H3N2) viruses are found in swine, they should be called “swine influenza A (H3N2)” viruses.

Another way of saying this is “swine H3N2”. If human infections with these viruses occur, these viruses are then called “variant” viruses as designated by the WHO because they are infecting a different species and are called “influenza A (H3N2)v” or just “H3N2v”.

Calling a pig influenza virus that contains genes from birds, pigs and people influenza viruses and infects people, “swine flu” is misleading because it refers to the virus being in pigs – swine H3N2.

When that virus crosses over and infects people, the accurate way to refer to it is “variant H3N2” or “H3N2v”.

This new standardized naming convention will allow the media to use more accurate terminology to communicate to consumers and will help reinforce to consumers that you cannot get the flu from eating or handling pork and pork products.