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A powerful influenza virus is spreading across northern India. Two-thirds of households in the area are impacted. Who is most vulnerable? And what steps can individuals take to safeguard themselves?

The Delhi metropolitan area in Northern India is witnessing a sharp rise in cases caused by the H3N2 influenza virus this autumn. The region, which includes numerous surrounding towns and districts in Haryana, Uttar Pradesh, and Rajasthan, is home to approximately 46 million people.

As per a survey conducted by the community-driven social media platform LocalCircles, 69% of families in the area have at least one member experiencing flu-like signs. Medical professionals indicate that H3N2 is the most common type of influenza in the region at present.

“The rising numbers indicate that the virus is spreading widely,” said Dr. Rituja Ugalmugle, a specialist at Wockhardt Hospitals in Mumbai Central, to the newspaper Indian Express. There are also reports of increasing case numbers from other states.

Who’s at risk

H3N2 infections typically begin with an abrupt high fever, chills, a sore throat, and a stuffy nose. Additional symptoms can involve a dry or mucus-producing cough, intense headaches, discomfort in the arms and legs, muscle aches, and significant tiredness and weakness. Certain patients, especially young children, might experience a loss of appetite, feelings of nausea, or digestive issues.

Children, the elderly, pregnant individuals, and those with long-term health issues like asthma, diabetes, and heart problems are often most severely affected. In most instances, the illness follows a pattern similar to a severe flu, and patients typically regain their health within a week.

Infections may result in severe issues like bronchitis, pneumonia, or the aggravation of pre-existing heart or lung problems. Medical facilities note that numerous individuals experience symptoms for a prolonged time or become ill enough to require hospitalization.

Unlike the typical cold or standard flu, H3N2, which isa type of Influenza A“, is often more intense and persists for a longer duration,” Dr. Mayanka Lodha Seth from Redcliffe Labs told the Indian Express.

If a patient begins to experience trouble breathing or chest pain, their lips or nails turn blue, they feel confused, or they are severely dehydrated, the infection can become life-threatening. Individuals showing these signs should seek immediate medical care. Additionally, they should contact a healthcare professional urgently if they develop a high fever following several days of treatment.

Necessary H3N2 precautions

Similarly to the coronavirus, medical professionals advise regular hand cleaning, wearing masks, steering clear of large gatherings, keeping a nutritious diet, and obtaining the most recent annualflu vaccine.

There is no particular treatment for H3N2. Physicians typically manage the patient’s symptoms through bed rest, adequate hydration, and medication to reduce fever. In severe cases or for individuals at higher risk, antiviral drugs may be prescribed.

“The current seasonal H3N2 emerged from the 1968 influenza pandemic. It developed by combining with an avian H3 virus,” said Dr. Martin Beer, vice president of the Friedrich Loeffler Institut (FLI), Germany’s national institute for animal health. “Therefore, the adaptation processes occurred a long time ago, and the ‘avian’ components, such as H3, date back to that period.”

Since that time, many different forms of the H3N2 strain have spread around the world. They reappear regularly as waves of seasonal influenza, typically with genetic changes in specific regions. “Yearly spread and immune system pressure lead to the adaptation of seasonal flu viruses, and we address them by developing new vaccines. Therefore, currently, with the seasonal H3N2 virus, it’s not about adaptation from birds to humans, but rather ongoing improvement within the human body,” Beer explained.

A research paper released in February 2024 looked into modifications in the receptor preference of H3N2 influenza viruses between 1990 and 2000. It discovered that the way the human H3N2 influenza virus attaches to human receptors has evolved over recent decades, resulting in a lengthening of the receptor-binding area. This elongation facilitates the virus’s ability to adjust to new hosts or tissues, potentially enhancing its spread. Additionally, it helps the virus bypass both immune responses and therapeutic interventions.

Over the course of fifty years, evolution has left clear and understandable signs of adaptation,” Beer stated. “The first, and most significant, change occurred fifty years ago, which contributed to the pandemic of that era. Since then, H3N2 has resurfaced in seasonal outbreaks with varying degrees of severity. In certain years and regions, it has been particularly prevalent compared to other influenza strains, resulting in a higher number of cases accordingly.

Reports from monitors and the World Health Organization (WHO) suggest that the current risk of a pandemic is low, as long as there are no major changes in the virus’s structure or how it spreads. Nevertheless, flu viruses like H3N2 can evolve rapidly, which is why authorities are keeping a close watch.

If the H3N2 strain were to change in a manner that increases its ability to pass between people or bypass current immunity, it might spread rapidly, potentially causing an outbreak or global pandemic. For this reason, scientists closely monitor influenza viruses to prepare for the most severe possibilities.

This piece was initially composed in German.

Author: Alexander Freund