NEW DELHI: The recent spurt in H1N1, or swine flu, cases in the country is not due to a new strain, official sources said on Sunday, adding that there is no need to panic as the strain has been in existence.
According to senior scientists at the Indian Council of Medical Research (ICMR), the Influenza A (H1N1) pdm09 viruses currently circulating in the country belong to the A/Missouri/11/2025 (H1N1) pdm09-like virus strain.
“These viruses belong to clade 6B.1A.5a2a, subclade D.3.1.1, and have been in circulation since 2025,” they said.
Emphasising that there is no new strain of H1N1, which has been identified for the spurt in cases, especially in Delhi and adjoining areas, the sources said that the Influenza strains currently circulating are also well matched with the vaccine strains recommended for the Northern Hemisphere.
“The situation continues to be closely monitored through regular surveillance, and necessary public health measures are being undertaken,” the sources added.
Seasonal influenza, including H1N1, is mostly self-limiting. Common symptoms include fever, cough, headache and body ache, and most people recover with appropriate care and rest.
If symptoms persist, worsen or become severe, timely consultation with a doctor is advised, experts said.
According to Dr Rajeev Jayadevan, former president of the Indian Medical Association (IMA), Cochin, Influenza is a seasonal disease caused by a group of viruses, among which H1N1 was identified as driving the Delhi surge this year.
“H1N1 is not a new virus like SARS-CoV-2. However, over time, all influenza viruses undergo evolutionary changes called mutations. These can occur either gradually or in sudden bursts,” he told TNIE.
Giving further details, he said, "Imagine a novel with many chapters. A few spelling mistakes do not change the story; this process is called antigenic drift. These minor genetic changes enable the virus to infect people repeatedly. On the other hand, if we change entire chapters, the story itself might change. Much less common, this is called antigenic shift, which can sometimes result in a more dangerous version of the virus."
He, however, said there is no evidence of any large-scale changes among human influenza viruses this year.
“The circulating strain is well-known from previous years, spreading more during the humid, congested conditions of the monsoon season,” he added.
The disease is mild in most cases, but it can occasionally turn severe in vulnerable individuals such as the elderly, children, pregnant women and those with certain health conditions.
Dr Jayadevan said that flu shots provide moderate-range protection from infection with the virus, and long-range immunity against severe outcomes like death.
“Antivirals help high-risk patients, while symptomatic care is enough for others. Antibiotics are not required,” said Dr Jayadevan, who is the co-chairman of the National IMA Covid Task Force.
He advised people to take preventive measures like avoiding crowds, wearing masks in closed, ill-ventilated spaces, and washing hands after visiting public places.
“Staying home when feverish and avoiding unnecessary hospital visits also prevent the virus from reaching more people,” he further said.
