No new H1N1 strain identified; what we're seeing is seasonal influenza uptick: Former WHO Chief Scientist

Experts attribute rise in H1N1 cases to seasonal flu, not a new strain

Amid rising concerns over the number of H1N1 influenza cases in several Indian cities, public health experts have moved to reassure the public that the current upswing is a seasonal pattern rather than the arrival of a new virus.

Former World Health Organisation (WHO) Chief Scientist Dr Soumya Swaminathan said in an interview with ANI on Sunday that the increase is a seasonal influenza uptick and there is no cause for panic, as no new strain has been detected. She explained that influenza cases typically rise during the monsoon season in India and continue into winter, and that improved surveillance systems are helping identify circulating viruses more effectively.

"What we're seeing is a seasonal influenza uptick. We see this every year," Dr Swaminathan said. "The doctors feel that this year it has started a little earlier, but normally in India, we do have a monsoon seasonal increase in influenza cases, and then it continues into winter."

She pointed to the H1N1 Michigan strain, which has been circulating since the 2009 pandemic, as the cause of the current rise, and emphasised it is not a new variant. "I think we need to reassure people that this is not a new strain. It is not more transmissible or more virulent," she added.

Dr Swaminathan also credited increased awareness, testing and diagnostic facilities with resulting in more reported cases from cities including Delhi and Bengaluru.

ICMR confirms seasonal rise with H1N1 accounting for almost all Influenza A cases

Indian Council of Medical Research (ICMR) Director General Dr Rajiv Bahl made similar remarks during a media briefing on Tuesday, describing India as witnessing a seasonal rise in respiratory infections, driven primarily by Influenza A subtype H1N1, with minor circulation of H3N2, Influenza B (Victoria lineage), and mild SARS-CoV-2 cases.

Dr Bahl said H1N1 accounts for nearly 98% of circulating Influenza A cases, with H3N2 making up the rest. He confirmed that 98-99% of all cases remain mild, self-limiting, and manageable at home with rest, hydration and basic care.

"There should not be any cause of panic that we can see, any cause of concern. It is a large number of cases with the same H1N1 strain, which is the seasonal influenza," Dr Bahl said.

Preventive measures: hygiene over masks, antivirals remain but what about the vaccine

Instead of masks, Dr Bahl advised standard hand hygiene, respiratory etiquette, and maintaining a distance of one to two metres from symptomatic individuals to avoid respiratory droplets. He stated that the respiratory droplet infections travel at most one to two meters, explaining why masks are not being recommended.

Regarding vaccines, Dr Bhal said high-risk groups—including adults aged 65 and above, pregnant women, and immunocompromised individuals—can opt to take the Northern Hemisphere flu vaccine in consultation with their physicians. However, a cost-effectiveness analysis in India means there is no decision to make it universal under the national immunisation programme.

the current circulating strains remain sensitive to standard antivirals like oseltamivir, but Dr Bahl strictly discouraged the unprescribed use of antivirals and antibiotics, as antibiotics are ineffective against viral illnesses.

High-risk groups and symptoms

Dr Swaminathan identified symptoms of H1N1 such as fever, body ache, sore throat, headache, and fatigue, lasting 4-5 days up to a week for most people. She stressed that most recover with rest, paracetamol, and plenty of hot fluids.

High-risk groups for serious complications include those above 65, children under 5, pregnant women, and immunocompromised individuals. Dr Swaminathan also noted that the circulating strain is not more transmissible or more virulent than previous strains.

Surveillance and outbreak tracking

The ICMR has clarified that no new strain of Influenza A (H1N1) has been identified in India. The currently circulating H1N1 viruses are similar to the A/Missouri/11/2025 (H1N1) pdm09-like virus strain, belonging to clade 6B.1A.5a2a and its subclade D.3.1.1. The ICMR also described that strains currently circulating are well matched with the vaccine strains recommended for the Northern Hemisphere.

Real-time surveillance is tracking trends across 73 sentinel hospitals and 167 virus research and diagnostic laboratories nationwide, according to Dr Bahl. He said the health ministry has been reviewing the situation, with Union Health Minister J.P. Nadda having chaired a high-level review on the epidemiological situation and public health preparedness on 21 August, as per Livemint.

Data reported to the ICMR indicated that Delhi has reported over 2,600 influenza cases this year, with H1N1 accounting for 70-75% of total infections. Other significantly affected states include Karnataka, Maharashtra, and Kerala.

Perspectives

• Public health officials' viewpoint: Maintain calm and highlight that the seasonal rise is expected, that the strains are not new, and that most cases are mild and manageable at home. Emphasis is on hygiene over masks, and on the availability of vaccines for certain groups.
• Health ministry/regulatory response: Enhance and support surveillance, communicate practical guidance, and coordinate a high-level review to prepare, while keeping the public informed without causing alarm.