H3N2 Virus Symptoms, Treatment and Prevention

H3N2 Virus: What You Need to Know About This Flu Strain

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The flu season is here and one of the strains that are circulating this year is the H3N2 virus.

This virus is a subtype of influenza A, which is an important cause of human influenza. H3N2 viruses can infect birds and mammals, and they can mutate into different strains over time.

In this blog post, we will answer some common questions about the H3N2 virus, such as:

  • What are the symptoms of H3N2 infection?
  • How is H3N2 diagnosed and treated?
  • How effective is the flu vaccine against H3N2?
  • How can you prevent H3N2 infection?

Symptoms of H3N2 Infection

The symptoms of H3N2 infection are similar to those of other seasonal influenza viruses.

They typically appear suddenly and can include:

  • Fever
  • Cough
  • Sore throat
  • Runny or stuffy nose
  • Muscle or body aches
  • Headache
  • Fatigue
  • Sometimes, vomiting and diarrhea (more common in children than adults)

The symptoms of H3N2 infection can last for a week or longer and they can be severe, especially in older adults and younger children.

Some people may develop complications from H3N2 infection such as pneumonia, bronchitis, sinus infections, ear infections, or worsening of chronic medical conditions.

In rare cases, H3N2 infection can lead to death.

Diagnosis and Treatment of H3N2 Infection


If you have symptoms of the flu you should see your doctor as soon as possible. Your doctor may perform a rapid flu test to confirm if you have H3N2 or another flu strain.

The test involves swabbing your nose or throat and getting the results within minutes.


The treatment of H3N2 infection depends on your age, health status, and severity of symptoms.

Most people with mild symptoms can recover at home by resting, drinking plenty of fluids, and taking over-the-counter pain relievers and fever reducers.

However, some people may benefit from antiviral medications, which can shorten the duration and severity of symptoms and reduce the risk of complications. Antiviral medications are most effective when taken within 48 hours of symptom onset.

Antiviral medications for H3N2 infection include oseltamivir (Tamiflu), zanamivir (Relenza), peramivir (Rapivab), and baloxavir (Xofluza).

These medications are available by prescription only and may have side effects such as nausea, vomiting, headache, or allergic reactions. You should consult your doctor before taking any antiviral medications.

Effectiveness of the Flu Vaccine Against H3N2

The flu vaccine is the best way to prevent influenza infection and its complications. The flu vaccine is updated every year to match the strains that are expected to circulate during the flu season.

The flu vaccine for the 2021/22 season contains four strains: two influenza A strains (H1N1 and H3N2) and two influenza B strains.

The effectiveness of the flu vaccine varies from year to year depending on how well it matches the circulating strains and how many people get vaccinated.

According to the Centers for Disease Control and Prevention (CDC), the flu vaccine for the 2020/21 season was 39% effective overall against any influenza virus and 34% effective against H3N2 specifically.

The effectiveness of the flu vaccine against H3N2 may be lower than other strains because H3N2 viruses tend to adapt to growth in eggs more readily than other types of flu viruses.

These egg-adapted changes can reduce the effectiveness of the vaccine strain. However, even if the vaccine is not a perfect match for H3N2, it can still provide some protection and reduce the severity of illness.

Prevention of H3N2 Infection

Besides getting vaccinated there are other ways to prevent H3N2 infection and stop its spread.

These include:

  • Washing your hands frequently with soap and water or using an alcohol-based hand sanitizer
  • Covering your mouth and nose with a tissue or your elbow when you cough or sneeze
  • Avoiding touching your eyes, nose, and mouth with unwashed hands
  • Staying away from people who are sick or have symptoms of the flu
  • Staying home if you are sick or have symptoms of the flu
  • Cleaning and disinfecting frequently touched surfaces and objects
  • Wearing a mask or a face covering when you are in public or around people who are not from your household
  • Getting enough sleep, eating a balanced diet, and staying physically active to boost your immune system


H3N2 is a subtype of influenza A virus that can cause severe flu symptoms and complications.

The best way to prevent H3N2 infection is to get vaccinated every year and follow good hygiene practices.

If you have symptoms of the flu, you should see your doctor as soon as possible and take antiviral medications if prescribed.

By taking these steps, you can protect yourself and others from H3N2 and other flu strains.

Frequently Asked Questions

What is H3N2 virus?

H3N2 virus is a subtype of influenza A virus that causes respiratory illness in humans and animals.

How is H3N2 virus transmitted?

H3N2 virus can be transmitted from animals (mainly pigs) to humans, or from humans to humans through respiratory droplets or contact with contaminated surfaces.

What are the symptoms of H3N2 infection?

The symptoms of H3N2 infection are similar to other types of flu, such as fever, cough, sore throat, runny nose, headache, body aches, fatigue, diarrhea, and vomiting.

How is H3N2 infection diagnosed?

H3N2 infection can be diagnosed by a laboratory test that detects the presence of the virus or its antigens in a nasal or throat swab sample.

How is H3N2 infection treated?

H3N2 infection can be treated with antiviral medications that can reduce the severity and duration of symptoms if taken within 48 hours of onset. These medications include oseltamivir (Tamiflu), zanamivir (Relenza), peramivir (Rapivab), and baloxavir marboxil (Xofluza).

How can H3N2 infection be prevented?

H3N2 infection can be prevented by getting vaccinated against seasonal flu every year, as the vaccine may offer some protection against H3N2 strains. Other preventive measures include avoiding contact with sick people or animals, washing hands frequently, covering coughs and sneezes, and staying home when sick.

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