Influenza A H3N2 variant (H3N2v) virus
Between August and December of 2011, 12 U.S. residents were found to be infected with an influenza A H3N2 variant virus (H3N2v). This virus also has been found in swine (pigs) in many states.
Investigations into the human cases revealed that some of the infections in humans came after the person had contact with swine, and a few from human-to-human transmission. In April 2012, a case of H3N2v was detected in a child. Then, beginning in July 2012, multiple H3N2v human infections were identified.
What is a Variant Influenza A Virus?
Type A influenza viruses commonly infect many species of animals, including swine and water birds. The viruses cause regular outbreaks among these animals. Type A influenza viruses can easily change, creating new virus strains. Some of these new virus strains can infect humans.
A virus that normally circulates in swine but can be found in humans is called “variant.”
Most type A influenza viruses that infect animals are very different from human (seasonal) influenza viruses. This is true of current H3N2 viruses. While these variant influenza viruses seldom infect humans, such infections can and do occur. In fact, influenza viruses can spread both from swine to humans and from humans to swine.
How Variant Influenza Viruses Spread
These infections have been most likely to occur when people are in direct contact with infected swine, such as in swine barns and livestock exhibits housing swine at fairs. This kind of transmission is thought to occur in the same way that seasonal flu transmits in people, which is mainly through coughing or sneezing by people who are infected. People also may become infected by touching something with flu viruses on it and then touching their mouth or nose.
In most cases, variant flu viruses have not shown the ability to spread easily and sustainably from person-to-person.
Take Action to Prevent the Spread of Flu Viruses Between People and Swine
- 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, and don’t take food or drink into animal areas.
- Young children, pregnant women, people 50 and older and people with weakened immune systems should be extra careful around animals.
- 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 swine if you are experiencing flu-like symptoms.
If you must come into contact with swine while you are sick, or if you must come in contact with swine that are 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.
Frequently Asked Questions
- Is it safe to eat pork? Yes. H3N2 variant has not been shown to be transmissible to people through eating pork or other products derived from swine.
- What symptoms do people have when they are infected with variant viruses? People who have been infected with variant viruses have had symptoms similar to the symptoms of regular human seasonal influenza. These include fever, tiredness, lack of appetite and coughing. Some people also have reported runny nose, sore throat, eye irritation, nausea, vomiting and diarrhea.
- What should I do if I get sick?If you have visited an area where H3N2v or other variant virus infections have been identified recently and you develop flu-like illness, with a fever of 100°F or higher, contact your healthcare provider (a doctor, physician’s assistant, nurse practitioner, etc.). Tell them if you have had contact with swine or with other sick people.
Whenever you have flu symptoms remember to tell your healthcare provider if you have asthma, diabetes, heart disease, neurological and neurodevelopmental conditions, are pregnant, or are older than 50 or (if patient is your child) younger than 5 years. These conditions and age factors (and others) put you at high risk of serious complications if you get the flu. Healthcare providers will determine whether influenza testing and treatment are needed.
- Where can I go to get more information?
- DHEC monitors influenza activity and makes this information available in our weekly Flu Watch report.
- Information that DHEC provides to physicians and healthcare providers about what to look for regarding Influenza A H3N2v can be found at our Health Alert Network homepage.
- Get information on rapid influenza testing for H3N2v from the CDC’s Morbidity and Mortality Weekly Report.
- Information about Influenza A H3N2v at the national level can be found at the CDC H3N2v website.
- Get interim guidance on case definitions to be used for investigations of Influenza A H3N2v virus.
- Information and materials, including educational posters that can be displayed around animal exhibits, are available in the Compendium of Measures to Prevent Disease Associated with Animals in Public Settings, 2011, available via the National Association of State Public Health Veterinarians website.
- Find guidance for school administrators dealing with potential outbreaks of H3N2v from the CDC.
If, after reading the information available on our website, you have questions about the vaccine,
please call 1-800-27SHOTS (1-800-277-4687).