Northern India, in particular the Delhi metropolitan region, is experiencing a significant spike in infections with the H3N2 strain of this autumn. There are about 46 million people in the conurbation around the Indian capital, which extends across many neighboring towns and districts in the states of Haryana, Uttar Pradesh and Rajasthan.
According to a survey by the community-based social media platform LocalCircles, 69% of households in the area currently have at least one person with flu-like symptoms. Doctors say H3N2 is currently the predominant influenza variant in the region.
“The increasing numbers make it clear that the virus is circulating extensively,” Dr. Rituja Ugalmugle, a consultant at Wockhardt Hospitals in Mumbai Central, told the newspaper Indian Express. Reports of growing numbers of cases are also coming in from other states.
Who’s at risk
H3N2 infections often start with a sudden high fever, shivering, a sore throat and a runny nose. Other symptoms may include a dry or productive cough, bad headaches, aching arms and legs, muscle pains, and severe fatigue and weakness. Some patients, particularly children, may lose their appetite, feel nauseous, or have gastro-intestinal problems.
Children, the elderly, pregnant people, and people with chronic conditions such as asthma, diabetes and heart issues tend to be hit hardest. In most cases, disease progression is that of a typical but nasty flu, and patients usually recover within a week.
Infection can lead to serious complications such as bronchitis, pneumonia, or a worsening of existing heart or lung conditions. Hospitals report that many people exhibit symptoms for an extended period or become so sick that they have to be admitted.
“Unlike the common cold or regular flu, H3N2, which is , is often more severe and tends to last longer,” Dr. Mayanka Lodha Seth of Redcliffe Labs told the Indian Express.
The infection becomes dangerous if the patient starts to have difficulty breathing or develops chest pains, their lips or nails turn blue, they become confused, or they are very dehydrated. Anyone experiencing these symptoms should get treatment immediately. They should also seek urgent medical assistance if they have a high fever after being treated for several days.
Necessary H3N2 precautions
As with the , doctors recommend frequent hand-washing, masking, avoiding crowds, maintaining a balanced diet and getting the latest annual .
There is no specific therapy for H3N2. Doctors will usually treat the patient’s symptoms with bed rest, plenty of fluids, and medicine to lower the fever. Serious cases and high-risk patients may be given anti-viral medication.
“The current seasonal H3N2 emerged from the 1968 influenza pandemic. It developed by combining with an ,” said Dr. Martin Beer, vice president of the Friedrich Loeffler Institut (FLI), Germany’s Federal Institute for Animal Health. “So the adaptation processes took place a long time ago, and the ‘avian’ components, like H3, are from that time.”
Since then, numerous variants of the H3N2 subtype have circulated globally. They return periodically as waves of seasonal flu, often with regional genetic mutations. “Annual circulation and immune pressure result in the adaptation of seasonal flu viruses, and we respond to them with new vaccines. So these days, with the seasonal H3N2 virus, it’s no longer a case of adaptation from avian to human, but of continual optimization within the human host,” Beer told DW.
A study published in February 2024 examined changes in the receptor specificity of H3N2 influenza viruses from 1990 through 2000. It found that the binding behavior of the human H3N2 influenza virus to human receptors had changed over the last few decades, leading to an extension of the receptor-binding site. This extension makes it easier for the virus to adapt to new hosts or tissue, and can increase transmissibility. It also makes it easier for the virus to evade both and treatments.
“Fifty years of evolution leave visible and comprehensible traces of adaptation,” Beer said. “The first, and most important, shift happened 50 years ago, and led to the pandemic at the time. Since then, H3N2 has returned in seasonal waves and at differing levels of intensity. In some years, in some regions, it’s very dominant compared to other influenza variants, which can lead to a correspondingly high number of cases.”
Assessments by monitors and the World Health Organization (WHO) indicate that there is currently a low risk of a pandemic, provided there is no significant change in the structure of the virus and its transmission pathways. However, influenza viruses such as H3N2 are capable of mutating very quickly, so officials are remaining vigilant.
Should H3N2 mutate in such a way as to become more transmissible from human to human, or able to evade existing immunity, it could spread suddenly and quickly, which could lead to an epidemic or pandemic. Scientists therefore keep a very close eye on influenza viruses so they can react to worst-case scenarios.
This article was originally written in German.
The post H3N2 influenza spreads rapidly in Delhi, northern India appeared first on Deutsche Welle.
