ICMR Confirms No New H1N1 Strain in India

The Indian Council of Medical Research (ICMR) stated on 23 August 2026 that no new strain of Influenza A (H1N1) has been identified in India. The circulating Influenza A (H1N1) pdm09 strain was described as similar to the A/Missouri/11/2025 (H1N1) pdm09-like virus, which belongs to clade 6B.1A.5a2a and subclade D.3.1.1.

Influenza A (H1N1) and pdm09 lineage

Influenza A is a genus of Orthomyxoviridae viruses, and H1N1 is a subtype defined by haemagglutinin 1 and neuraminidase 1 surface proteins. The term pdm09 refers to the 2009 pandemic H1N1 lineage, which has continued to circulate in seasonal influenza patterns after 2009.

Virus classification and vaccine matching

ICMR scientists stated on 23 August 2026 that the circulating strains have been in circulation since 2025. They also stated that these strains remain well-matched with the vaccine strains recommended for the Northern Hemisphere.

Seasonal influenza: symptoms and risk groups

Seasonal influenza is an acute respiratory infection caused by influenza viruses, and it commonly produces fever, cough, headache, and body aches. Most patients recover with rest, while young children, the elderly, and persons with underlying medical conditions face a higher risk of complications.

Important Facts for Exams

• Influenza A viruses are classified by haemagglutinin and neuraminidase proteins, such as H1N1 and H3N2.
• The 2009 H1N1 pandemic virus is commonly referred to as H1N1 pdm09.
• Clade and subclade names are used in influenza surveillance to track genetic changes in circulating viruses.
• Seasonal influenza cases often rise during the monsoon period because of humidity, temperature changes, and indoor crowding.

Public health review and hospital preparedness

The ICMR clarification followed a high-level health review meeting chaired by Union Health Minister JP Nadda and attended by Delhi Health Minister Pankaj Kumar Singh. The meeting assessed hospital preparedness for vector-borne and seasonal diseases.

Influenza surveillance in India

Influenza surveillance in India involves laboratory confirmation, virus characterisation, and monitoring of circulating strains. Delhi seasonal influenza figures reported on 23 August 2026 varied across media accounts, with one set of figures citing 1,777 confirmed H1N1 cases out of 2,392 Influenza-A infections and another citing 2,602 total influenza cases with H1N1 accounting for more than two-thirds.