The ICMR conducts continuous surveillance for diseases caused by respiratory viruses through its network of Virus Research and Diagnostic Laboratories (VRDLs) across the country.
Doctor Nivedita Gupta, the head of epidemiology at ICMR, told TOI that surveillance data from 30 VRDLS, from December 15 to date, suggested an increase in the number of influenza A H3N2 cases. “About half of all hospitalized severe acute respiratory infections (SARI) and outpatient influenza illnesses were found to have influenza A H3N2,” she said.
Dr. Gupta said the wave of infections caused by the virus subtype is expected to decrease from late March or the first week of April as temperatures begin to rise.
According to the ICMR, among hospitalized patients with H3N2, 92% of patients had fever, 86% had cough, 27% shortness of breath, 16% wheezing. Additionally, ICMR monitoring revealed that 16% of these patients had pneumonia and 6% had seizures.
“About 10% of patients with severe acute respiratory infections caused by H3N2 needed oxygen and 7% needed intensive care,” said health research agency Apex.
Dr Satish Koul, director of internal medicine at Fortis Memorial Research Institute in Gurgaon, said H3N2 is known to cause more severe symptoms than other flu viruses. “It’s not a new variant though. It has been in circulation for decades. The H3N2 flu subtype actually caused a massive outbreak in Hong Kong in 1968,” Dr Koul said.
He explained: “Infections caused by H3N2 are particularly different from normal influenza in that the clinical course of the disease is much more severe. It always starts with a high fever accompanied by chills and also causes an incessant cough.
Dr Rommel Tickoo, who heads the internal medicine department at Max Sake, said over the past two months they have been inundated with patients with feverish illnesses and coughs. “Many patients require hospitalization, which is unusual for illnesses caused by seasonal flu. The elderly and people with comorbidities are the most affected,” he added.
According to the World Health Organization (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 flu every year globally.
The most effective way to prevent the disease is vaccination, according to the United Nations health body. “In addition to vaccination and antiviral treatment, public health management includes personal protective measures such as regular hand washing with proper hand drying, good respiratory hygiene – covering mouth and nose when coughing or when sneezing, using tissues and disposing of them properly, self-isolating from those who feel unwell, feverish and showing other flu symptoms and avoid close contact with sick people among others,” adds- he.