Explained | All about H3N2 virus: symptoms, prevention, and cure

As H3N2 infection spreads through India, experts suggest masking up and practising social distancing.

Updated - March 18, 2023 12:15 pm IST

Published - March 16, 2023 12:39 pm IST

File photo: Women wearing face masks as a precaution against H3N2 virus cases on the rise in Hyderabad on Thursday, March 09, 2023

File photo: Women wearing face masks as a precaution against H3N2 virus cases on the rise in Hyderabad on Thursday, March 09, 2023 | Photo Credit: Nagara Gopal

The story so far: At least two people have succumbed to the H3N2 subtype of seasonal influenza in India, the Health Ministry confirmed last week. A countrywide surveillance has found at least 451 confirmed cases of H3N2 this year so far.

“India every year witnesses two peaks of seasonal influenza – one from January to March and other in the post-monsoon season. The cases arising from seasonal influenza are expected to decline from March end,” the Ministry said.

What is H3N2?

The influenza A virus is known to cause seasonal flu disease in humans. These are divided into subtypes based on two proteins found on the surface of the virus: hemagglutinin (H) and neuraminidase (N). There are 18 H-subtypes and 11 N-subtypes. More than 130 influenza A subtype combinations have been identified in nature so far, but virus reassortment, a process by which influenza viruses swap genetic information, makes many more subtypes possible, the U.S. Centres for Disease Control and Prevention said.

The H3N2 subtype appears to cause more hospitalisations than other influenza subtypes, India’s Ministry of Health and Welfare noted. About half of all inpatient severe acute respiratory infections (SARI) and outpatient illnesses displaying influenza-like symptoms seen in surveillance data collected between December 15, 2022, and March 10, 2023, were found to have been H3N2 infections.

Out of the SARI patients infected with H3N2, 10% needed oxygen, and 7% needed ICU support.


Infection by the H3N2 subtype of influenza A virus presents with classic flu symptoms that are also similar to COVID-19 symptoms – fever, cough, body ache, breathlessness, wheezing and pneumonia.

Seasonal influenza can also cause severe cough that can last around two or more weeks, although most patients recover within a week without medical intervention.

Also read | What you need to know about the H3N2 influenza virus currently circulating in India | In Focus podcast

According to the World Health Organisation (WHO), pregnant women, children under five years of age, the elderly, individuals with chronic medical conditions — like chronic cardiac, pulmonary, renal, metabolic, neurodevelopmental, liver or hematologic diseases, and individuals with immunosuppressive conditions — those with HIV/AIDS, receiving chemotherapy or steroids, or with malignancy, are at a greater risk of developing a severe form of flu, including that from the H3N2 subtype.

Is there a cure?

WHO recommends using oseltamivir (tamiflu) for H3N2 infection. The drug is made available free of cost through public health systems, the health ministry said.

The sale of oseltamivir in India is allowed under Schedule H1 of the Drugs and Cosmetics Act, 1940.


According to experts, washing hands with soap and water is the best way to prevent infection from the H3N2 subtype. The government has also advised citizens to wear masks and practise social distancing to avoid infection.

Covering mouth and nose while sneezing and coughing, avoiding touching eyes and nose, and drinking fluids are other ways to prevent H3N2 infection, the Health Ministry said in a press release. The ministry also advised against taking antibiotics or other medication without consulting doctors.

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