No new H1N1 strain, say ICMR sources amid swine flu surge in Delhi, other parts of India

ICMR Rules Out New Strain as Delhi H1N1 Cases Top 2,000

Scientists at the Indian Council of Medical Research (ICMR) said on Sunday that no new strain of the Influenza A (H1N1) virus—commonly known as swine flu—has been identified in India, even as Delhi's caseload this year has crossed the 2,000 mark. The clarification came amid a sharp rise in infections in the national capital and other parts of the country.

According to a senior ICMR scientist, the viruses currently circulating in India are similar to the A/Missouri/11/2025 (H1N1) pdm09-like strain, belonging to clade 6B.1A.5a2a and subclade D.3.1.1, and have been in circulation since 2025. The scientist added that the strains are well-matched with the vaccine strains recommended for the Northern Hemisphere. "There is no cause for panic," the ICMR said in a statement.

Delhi has recorded over 2,300 Influenza-A cases this year, including 1,777 H1N1 cases as of Friday, according to reports. On Thursday alone, 114 H1N1 cases were confirmed. The number represents a significant jump from 229 cases in the corresponding period last year, prompting the Delhi government to issue a public health advisory urging masks in crowded places, regular handwashing, and covering the mouth when coughing or sneezing.

An ICMR scientist told The Indian Express that around 70% of all respiratory infections in Delhi over the last week were caused by H1N1, after a high number of infections over the previous four to five weeks. However, the scientist noted that numbers have been slowly declining over the last two weeks, with data for the current week not yet available.

Government Response and Preparedness

Union Health Minister JP Nadda chaired a review meeting on Friday to assess Delhi's preparedness for seasonal and vector-borne diseases, including influenza, dengue, and malaria. Delhi Health Minister Dr Pankaj Kumar Singh attended the meeting and briefed the Centre on surveillance measures and hospital readiness.

"We are prepared for any situation. There is no shortage of medicine, doctors, beds," Singh told reporters on Saturday. "Everyone will receive timely and appropriate treatment." The review covered trends in influenza-like illnesses and severe acute respiratory infections, testing, laboratory surveillance, and availability of beds, oxygen, ventilators, and medicines.

Nadda emphasized the need for public awareness of preventive measures such as respiratory hygiene and hand hygiene. The Delhi government has also issued an advisory asking residents to avoid spitting in public, maintain distance from those with respiratory symptoms, stay hydrated, and avoid unnecessary close contact when unwell.

Expert Views: No Mutation, Seasonal Pattern

Doctors and public health experts echoed the ICMR's reassurances. Dr S Chatterjee of Apollo Hospital told The Indian Express, "That's good news for us. It's good to know that the mutation has not happened." He cited pollution, environmental factors, monsoon conditions, and weakened immunity as possible contributors to the rise.

Dr Rommel Tickoo, a physician, said the ICMR clarification is reassuring, noting that H1N1 is part of the seasonal influenza spectrum and that the focus should be on vigilance rather than panic.

Dr Rajeev Jayadevan, former president of the Indian Medical Association (IMA), Cochin, explained that H1N1 is not a new virus like SARS-CoV-2. He described the evolutionary process: "Imagine a novel with many chapters. A few spelling mistakes do not change the story; this process is called antigenic drift." He added that minor genetic changes enable the virus to infect people repeatedly, but there is no evidence of large-scale changes among human influenza viruses this year. He noted that the virus spreads more during humid, congested monsoon conditions.

Experts reiterated that seasonal influenza, including H1N1, is mostly self-limiting, with common symptoms such as fever, cough, headache, and body aches. Most people recover with appropriate care and rest. However, young children, elderly individuals, and those with underlying medical conditions are at greater risk of complications. Doctors advise timely consultation if symptoms persist, worsen, or become severe.

Vaccine Recommendations and Prevention

Health authorities are emphasizing vaccination as a preventive tool. Director General of Health Services Dr Loveneesh G Krishna told ANI that vaccination can help decrease the severity of H1N1 infection. He cited preventive measures including masks, handwashing, ventilation, and vaccines.

The National Centre for Disease Control (NCDC) has recommended the Northern Hemisphere vaccine for the 2026-2027 influenza season. WHO's recommendations typically include two Influenza A strains—one of which this year is A/Missouri/11/2025 pdm09-like—and one Influenza B strain.

Max Healthcare stated that getting the flu vaccine is associated with a 60% lower likelihood of needing treatment for the flu. Several vaccine options are available in India: NASOVAC-S4, an intranasal live attenuated quadrivalent vaccine for individuals above 2 years (single 0.5 ml dose, 0.25 ml per nostril), is not recommended in pregnancy or certain medical conditions. VaxiFlu S, a trivalent inactivated intramuscular vaccine, is recommended from 6 months of age, with two doses at least 4 weeks apart for previously unvaccinated children aged 6 months to 9 years, and a single annual dose for others.

The Indian Medical Association, in a 2015 statement, recommended influenza vaccines for children above 6 months, adults over 50, patients with certain chronic disorders, pregnant females, and healthcare providers. It takes about two weeks after vaccination for antibodies to develop and provide protection.

India typically experiences two flu peaks each year—one between January and March and another after the monsoons. Flu infection usually resolves in three to seven days; people generally need only paracetamol if necessary and fluids. Red-flag symptoms such as shortness of breath, chest pain, or blue lips or nails warrant immediate medical attention.

WHO has previously reported that globally, Influenza A detections greatly outnumbered Influenza B, with A(H1N1)pdm09 predominating in Eastern Asia and North America among other regions during the reporting period.