H3N2 Influenza: Symptoms, Transmission & Treatment

Updated in March 2023

The H3N2 virus is one of the sub-types of the Influenza A virus, which is also known as type A. It i one of the most frequently-occurring causes of the common flu. It is very easily transmitted between people through droplets left in the air from sneezing or coughing. t.

The H3N2 virus, just like the H1N1 sub-type of influenza, triggers flu symptoms like headache, fever and nasal congestion. It is very important to maintain adequate hydration to help flush out the virus from the body. It is also advised to use medication that will help to manage symptoms, like acetaminophen or ibuprofen.

Although H2N3 is a sub-type of the Influenza A virus, it does not cause flu symptoms in people, as this virus is only found in animals. Therefore, it is most likely that your symptoms are related to the H3N2 or H1N1 viruses.

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Main symptoms

Symptoms of an H3N2 infection are the same as an H1N1 infection. These symptoms include:

  • High fever, over 38ºC (or 100.4ºF)
  • Body aches
  • Sore throat
  • Headaches
  • Sneezing
  • Coughing
  • Runny nose
  • Chills
  • Excessive fatigue
  • Nausea and vomiting
  • Diarrhea, which will more frequently occur in children
  • Muscle weakness

The H3N2 virus is more frequently identified in children and older adults, although it can also infect pregnant women and recently post-partum women fore frequently. It can also easily infect people with compromised immune systems or chronic diseases.

How transmission occurs

Transmission of the H3N2 virus happens very easily through droplets that remain suspended in the air when an infected person coughs, speaks or sneezes. It can also occur through direct contact with infected people or with indirect contact of infected objects.

Are H2N3 and H3N2 the same?

Although these are both sub-types of the Influenza A virus, H2N3 and H3N2 are not the same because they target different populations. H3N2 is found solely in people, while H2N3 is found solely in animals, and is not associated with infections in people.

What is the difference between H3N2 and COVID-19?

Although they are both acute respiratory diseases caused by a virus, the H3N2 flu and COVID-19 are two very distinct conditions. In addition to being caused by different viruses, the H3N2 virus that causes the flu, the SARS-CoV-2 that causes COVID-19, their respective starts and intensity are also different:

Symptoms are most intense in the first 48 hours Symptoms are most intense in the 5th and 6th day of infection
Intense fever and body aches in the first days of infection Low fever in the first days of infection which can gradually increase over time
Improves by the end of 7 days  Symptoms evolve over time, and can result in serious symptoms, like respiratory changes or clots

Although symptoms are similar, you should still consult a doctor for assessment of your symptoms and to evaluate whether you should complete a COVID-19 or flu swab.

Treatment options

Treatment for the flu caused by H3N2 aims to relieve associated symptoms, and therefore the following can be recommended:

  • Rest
  • Adequate hydration throughout the day
  • Light meals that are easy to digest
  • Use of medication like analgesics (e.g. acetaminophen) and anti-inflammatories (e.g. ibuprofen)
  • Use of anti-viral medication, in some cases, to decrease the development and growth of viral cells, like Tamiflu (Oseltamivir) or Relenza (Zanamivir). These should be taken as prescribed by your doctor.

In addition, it is important that while you are infected by H3N2, you should remain in isolation for 7 to 10 days to avoid transmission to other people.

How to prevent

To prevent H3N2 infection, you should avoid contact with anyone with flu-like symptoms. Infected people should remain in isolation for 7 to 10 days, so that they can avoid transmission of the virus to others. In addition, you should use a face mark and ensure adequate hand hygiene.

It is important to avoid staying inside closed environments with too many people. It is also a good idea to avoid bringing your hands to your eyes or mouth, and avoid staying too close to a person who is infected.

It is also possible to prevent transmission of this virus by getting the flu vaccine, which is made available every year. The flu vaccine protects against the H1N1, H3N2 and Influenza B viruses. People of all ages should receive the vaccine, but it should be particularly taken by children and older adults, as the virus is more common in these groups. The flu vaccine should be taken every year, as the virus mutates over time and can become resistant to previous vaccines.