The ICMR conducts continuous surveillance of illnesses caused by respiratory viruses through its network of Virus Research and Diagnostic Laboratories (VRDLs) across the country.
Dr Nivedita Gupta, the head of epidemiology at ICMR, told TOI that surveillance data from 30 VRDLS, from December 15 till date, suggested a rise in the number of cases of influenza A H3N2. “About half of all inpatient severe acute respiratory infections (SARI) and outpatient influenza like illness were found to have influenza A H3N2,” she said.
Dr Gupta said the spate of infections caused by the virus subtype were likely to reduce from March-end or April first week, as the temperature begins to rise.
According to the ICMR, in hospitalised patients with H3N2, 92% patients were found to have fever, 86% had cough, 27% breathlessness, 16% wheezing. Additionally, the ICMR surveillance found that 16% such patients had pneumonia and 6% had seizures.
“About 10% of patients suffering severe acute respiratory infections caused by H3N2 needed oxygen, and 7% required ICU care,” the apex health research agency said.
Dr Satish Koul, director, internal medicine, at Fortis Memorial Research Institute, Gurgaon, said H3N2 is known to cause more severe symptoms than the other influenza viruses. “This is not a new variant though. It has been in circulation for decades. Influenza subtype H3N2, in fact, caused a massive outbreak in Hong Kong in 1968,” Dr Koul said.
He explained: “Infections caused by H3N2 are peculiarly different from the normal influenza in a way that the clinical course of the sickness is much more severe. It always starts with a high-grade fever with chills and also causes incessant coughing.”
Dr Rommel Tickoo, who heads the internal medicine department at Max Saket, said for the last two months they have been flooded with patients suffering from febrile illness and cough. “Many patients require hospitalisation, which is unusual for illnesses caused by seasonal influenza. Elderly and people suffering from co-morbidities are most affected,” he added.
According to the World Health Organisation (WHO), about 3 to 5 million cases of severe illness and about 2.9 lakh to 6.5 lakh respiratory deaths are caused by seasonal influenza every year globally.
The most effective way to prevent the disease is vaccination, the UN health body says. “Apart from vaccination and antiviral treatment, the public health management includes personal protective measures like regular hand washing with proper drying of hands, good respiratory hygiene — covering mouth and nose when coughing or sneezing, using tissues and disposing of them correctly, early self-isolation of those feeling unwell, feverish and having other symptoms of influenza and avoiding close contact with sick people among others,” it adds.