Table of ContentsView AllTable of ContentsOverviewWhat Is H3N2?H3N2 EpidemicsSymptomsDiagnosis and TreatmentPrevention
Table of ContentsView All
View All
Table of Contents
Overview
What Is H3N2?
H3N2 Epidemics
Symptoms
Diagnosis and Treatment
Prevention
You may have heard the term H3N2 in the news or read about it online. But chances are you don’t know much about what it is and how it’s different from other types of flu. Adults who were around in 2009 are probably familiar withH1N1—the strain of flu that caused a pandemic and sickened millions around the world. But H3N2 is a little different.
This article discusses what H3N2 flu is, as well as its symptoms and how it’s diagnosed and treated.
Flu Overview
Each year there are variants of influenza that cause illness during the flu season. The virus mutates, making it difficult to predict which one will make people sick each year or even how severe the season will be.
When WHO officials choose the strains of influenza to include in the yearly flu vaccine, they choose two strains of influenza A (one variant of H1N1 and one variant of H3N2) and one strain of influenza B. (Before 2024, quadrivalent vaccines would include two strains of influenza B.)
These strains are chosen over six months before the flu season starts because it takes that long to manufacture and prepare those vaccines for distribution.
What Is the H3N2 Flu Virus?
H3N2 virus is a non-human influenza virus that normally circulates in pigs but can infect people. Viruses that normally circulate in pigs are “swine influenza viruses.” When these viruses infect humans, they are termed “variant” viruses.
The H3N2 virus was circulating in pigs in 2010 and was first detected in people in 2011. Since first being identified in humans in 2011, the H3N2 virus has caused infection in people yearly throughout the U.S.
H3N2 Flu Epidemics
Although flu symptoms are typically similar no matter the strain of influenza, history has shown that seasons in which H3N2 influenza A is the dominant strain are more severe.
At the beginning of the 2014 to 2015 flu season, a mutated version of H3N2 caused a majority of the flu in the United States. The mutated virus was different from the strain of H3N2 influenza A that was included in that season’s vaccine.
Unfortunately, that means the vaccine did not provide as much protection against the flu as it would have otherwise. However, that doesn’t mean it didn’t work at all.
How Flu Shots Work
H3N2 Flu Symptoms
Risk Factors for Complications
People who are at higher risk for developing flu-related complications include:
Symptoms of the Flu
H3N2 Flu Diagnosis and Treatment
Only your healthcare provider candiagnose you with the flu. A diagnosis is made based on symptoms you are experiencing, a physical exam, and sometimes a rapid flu test that is performed using a nasal or throat swab.
If your healthcare provider determines you have the flu, treatment can vary depending on your age, overall health, and length of time that you have been sick.
Antiviral medications, such as Tamiflu or Relenza, can help shorten the severity of your symptoms or the duration of your illness. They are most effective if taken within the first 48 hours of the onset of symptoms.
If you have been sick longer than 48 hours, your healthcare provider may decide that taking antiviral medications won’t really benefit you. You may also be told you don’t need an antiviral medication if you are not athigh risk for flu complications.
Even without antiviral medications, there are important things you can do to give your body a chance to recover, such as:
Taking antibiotics won’t helpunless you have a secondary bacterial infection, as these drugs don’t kill viruses.
Treatment Despite a Negative Rapid Flu Test
Ways to Prevent H3N2 Flu
Steps you can take to reduce the infection and spread of H3N2 between people are the same as other flu viruses:
These steps can help prevent the spread of flu between pigs and people:
Summary
H3N2 is one subtype of the influenza A virus that often causes significant illness. Flu seasons are often more severe when H3N2 is the dominant strain causing illness. Because the influenza virus changes so frequently it is hard to identify and treat—and even harder to develop a vaccine months in advance of flu season.
Symptoms are similar no matter what strain of influenza is circulating each year. Treatment may include antiviral medications if diagnosed early; otherwise, rest, lots of fluids, and OTC medications can help relieve symptoms.
9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Centers for Disease Control and Prevention.Types of Influenza Viruses.
Centers for Disease Control and Prevention.Selecting Viruses for the Seasonal Influenza Vaccine.
Centers for Disease Control and Prevention.Influenza A (H3N2) variant virus.
Oklahoma State Department of Health.Influenza A H3N2 variant (H3N2v).
LeMieux J.Some Bad Flu News: H3N2 Is A Major Player This Year. American Council on Science and Health.
Centers for Disease Control and Prevention.Flu Symptoms & Diagnosis.
Centers for Disease Control and Prevention.Flu Treatment.
Centers for Disease Control and Prevention.Healthy habits to help protect against flu.
U.S. Centers for Disease Control and Prevention: Department of Health and Human Services.How the Flu Virus Can Change: ‘Drift’ and ‘Shift’.
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