H3N2 influenza cases spike in Delhi

Over the past few months, Delhi and surrounding areas have seen a significant rise in H3N2 influenza cases. A subtype of the Influenza A virus, H3N2 is causing concern due to its longer recovery time and the potential for severe complications, particularly among vulnerable populations. H3N2, part of the Influenza A family, is a common cause of seasonal flu worldwide.

However, experts warn that this strain can be particularly challenging to recover from and presents a higher risk of complications, especially for children, the elderly, and people with pre-existing health conditions. In mid-September 2025, a survey showed that 69 per cent of households in the Delhi-NCR area had at least one family member with flu-like symptoms.

In August 2025, Holy Family hospital in Delhi recorded nearly 80 positive cases, with that number rising to nearly 100 cases in September. Unlike the regular cold, H3N2 often begins with a sudden high fever, sore throat, and runny nose.

In addition to these symptoms, patients frequently experience muscle aches, severe fatigue, and headaches. In more serious cases, the flu can progress to pneumonia, which can be life-threatening for those in high-risk groups.

According to Dr Mayanka Lodha Seth of Redcliffe Labs, "H3N2 is more severe and tends to last longer than the common cold or regular flu.” The flu can become dangerous if patients experience trouble breathing, chest pain, confusion, or extreme dehydration. If these symptoms develop, it is essential to seek medical attention immediately.

Health experts believe the rise in H3N2 cases is linked to several factors. The changing weather, with sharp temperature fluctuations, creates an environment in which viruses thrive.

Meanwhile, Delhi’s persistent air pollution is further weakening respiratory immunity, making it easier for infections to spread. H3N2 spreads primarily through respiratory droplets when an infected person coughs or sneezes. It can also spread by touching contaminated surfaces and then touching the face.

Experts urge the public to follow basic hygiene practices like frequent handwashing and wearing masks, especially in crowded spaces. H3N2 cases aren’t tracked individually because it’s a regular strain of seasonal flu. Instead of reporting each case, health authorities monitor general flu trends and which strains are most common.

In places like India, centers like the Integrated Disease Surveillance and Response network test for dominant strains, rather than reporting every case of H3N2. While there is no specific treatment for H3N2, early detection and prompt medical care can prevent severe complications. Flu vaccines, which are updated each year to account for changes in the virus, are crucial in protecting against H3N2 and other strains of influenza.