Home / Science / Health /  Should you be worried about the H3N2 virus?

Cases of influenza-A subtype H3N2 are on the rise, with a few deaths reported across India. The government says it’s keeping a close watch on the situation and has issued advisories. Is there cause for concern? Mint explains:

What is the H3N2 virus?

There are four types of flu viruses: A, B, C and D. Of these, only A and B are known to cause seasonal outbreaks or epidemics among humans. C causes mild illness and D doesn’t affect humans. There are over 130 subtypes of A, based on a combination of hemagglutinin (H) and neuraminidase (N) proteins, found in nature. H3N2 is one of the two A subtypes routinely circulating among humans, the other one being H1N1. Influenza B is another circulating strain. The 1968 Hong Kong flu, which killed millions, was caused by H3N2, whereas the 2009 Swine Flu pandemic came from a novel strain of the H1N1 virus.

Is the current flu outbreak unusual?

Not really. The World Health Organization (WHO) estimates that 1 billion flu cases occur every year, of which 3-5 million are severe, causing between 290,000 and 650,000 deaths. Most recently, Australia reported over 220,000 flu cases in 2022 and around 8,500 cases in the first two months of 2023. India, until 9 March, had a total of 3,038 cases reported this year, with H3N2 being the predominant subtype. Annual data on H1N1 infections in India suggests a sporadic pattern in the rise of cases, with a dip in 2020 and 2021. But 2022 saw 13,202 H1N1 cases compared to 778 in 2021 and 2,752 in 2020.

What caused the recent surge?

India reports flu cases throughout the year, with two peak seasons: post-monsoon and January-March. Experts say the rise in 2022 and 2023 could be because of a sudden increase in exposure to flu viruses once covid-appropriate behaviour, such as wearing masks and avoiding public places, were relaxed. Air pollution worsened the situation by damaging immune cells.

Which population groups are at risk?

Seasonal influenza infects (asymptomatically and symptomatically) one in five unvaccinated children and one in 10 unvaccinated adults. Five groups are high-risk: children aged 6-59 months, pregnant women, elderly, adults with comorbidity and health workers. WHO recommends the flu jab for these groups, but the coverage is rather low in India (only 1.5% of the elderly population). The government advised vaccination for health workers dealing with current H1N1 cases.

What are the remedies and precautions?

Those who get infected are given drugs that treat specific symptoms such as fever and cough. Antiviral drug (Oseltamivir) is only recommended for the high-risk population or in specific cases. Experts recommend wearing masks in crowded places, covering your mouth and nose with a handkerchief while sneezing or coughing, staying home if you feel sick, and frequent washing of hands. The cases will likely dip by March-end or mid-April as the temperature rises, according to some experts.

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