H3N2 is a subtype of the influenza A virus that has been responsible for two outbreaks of infection in the last 60 years. H3N2 is a major strain of seasonal flu every year and vaccines can provide some protection.
Different types of influenza (flu), such as influenza A and influenza B, cause yearly seasonal epidemics. The flu is a viral respiratory illness that is most prevalent in the fall and winter months.
The viruses that result in the flu can transmit when a person with the infection sneezes or coughs and droplets travel to another person’s nose or mouth.
This article explains H3N2, recent outbreaks, and how to recognize and protect against symptoms.
H3N2 is a major type of seasonal flu virus. According to
A 2018 review maintained that H3N2 was the main virus that doctors found in
There are 18 different hemagglutinin subtypes (H1–H18) and 11 different neuraminidase subtypes (N1–N11). H3 and N2 refers to the subtypes present on this strain of the flu virus. H3N2 is one of two main subtypes that pass between humans, along with H1N1.
In the U.S., the 2017/18 flu season was
The CDC tested 98,446 samples during this time. Of these:
- 53,790 tested positive for influenza (54.6%)
- 38,303 contained influenza A (71.2% of all the positive flu samples)
- 31,977 were H3N2 subtypes (84.9% of all influenza A samples)
In the U.S., clinicians first isolated H3N2 in a marine returning to San Diego from Vietnam. The first pandemic H3N2 flu season led to more than 100,000 deaths.
However, the pandemic also provided the first opportunity to test the effects of an antiviral medication — amantadine (Gocovri) — on people with flu. Although the effectiveness of amantadine was unclear, medical professionals used it in some later flu seasons.
In addition to treating influenza A viruses, amantadine can also help treat Parkinson’s disease.
The symptoms of H3N2 influenza are similar to other subtypes,
- pain and weakness
- a headache
- a cough that does not produce mucus
- a sore throat
- runny nose
However, complications may develop, including:
- bacterial pneumonia, a lung infection
- ear infections
- sinus infections
- chronic medical conditions getting worse, including congestive heart failure, asthma, or diabetes
Vaccines can provide a defense against all types of seasonal influenza. The CDC recommend them for the most at-risk groups for severe effects of flu,
- people aged over 65 years
- pregnant people
- those living with chronic diseases or compromised immune systems
- children under 5 years of age
Flu viruses can mutate over time, swapping genetic information with other viruses that occupy the same body. For this reason, research on the effectiveness of the H3N2 vaccine from 2016/2017 showed low effectiveness, reducing or preventing symptoms at a rate of
However, vaccines remain an important tool in reducing the spread and severity of flu. The contents of the vaccine change yearly to try to match the season’s predicted flu strains.
Most people with flu will not need treatment as the symptoms are often mild and resolve in a few days.
They are most effective when people take them within 2 days of symptoms starting, according to the CDC. A course usually lasts for 5 days.
Vaccines can help a person prevent flu. However, other measures help to reduce exposure to H3N2 and other seasonal flus,
- keeping a distance from people who show symptoms of sickness
- covering the mouth and nose during coughs and sneezes
- washing the hands thoroughly and often
- avoiding touching the eyes, nose, or mouth
- practicing other good health habits, such as cleaning and disinfecting surfaces, getting regular exercise and adequate sleep, and having a healthy eating plan
H3N2 flu is a type of flu that has links to more severe flu seasons. It first emerged in humans during a 1968 pandemic. However, different mutations have emerged since, particularly during the 2017/2018 flu season. Its symptoms are similar to other types of flu.
Recent studies on H3N2 vaccines have shown low effectiveness, but they can still help to reduce symptom severity and the risk of complications in at-risk populations.
People can slow or prevent transmission by practicing regular handwashing, covering the mouth and nose when coughing or sneezing, and avoiding physical contact with people who have flu.