Weak immunity, low vaccination, pollution behind H3N2 surge

NORTH India witnessed one of the most severe outbreaks of H3N2 influenza in recent years, with hospitals across Delhi-NCR and adjoining states reporting a surge in cases of high fever, cough, and body ache. Doctors say the outbreak has been fuelled by a combination of environmental factors, weakened post-pandemic immunity, and low vaccination coverage — turning what was once a seasonal flu into a prolonged public health concern.

- ASHISH SRIVASTAVA @New Delhi

“The situation this year is worrisome,” said Dr Ankita Baidya, head of infectious diseases at Manipal Hospitals, Dwarka. “Post the Covid-19 pandemic, our immunity has weakened, making us more vulnerable. The lack of awareness around adult vaccination and the fact that many people haven't taken vaccines against the current circulating strains, which are more virulent, have contributed to the surge.”

She added that crowded public spaces, poor ventilation, and rising air pollution levels are worsening respiratory symptoms and accelerating the spread of the virus. “We are still seeing a steady number of flu cases in OPDs. While most patients have mild symptoms, those with comorbidities such as diabetes, heart problems, or lung diseases are coming in with more severe illness,” she said.

Vulnerable groups