No new strain of H1N1 in India, says ICMR

• The Indian Council of Medical Research (ICMR) said no new strain of H1N1 has been identified and there is no cause for panic, amid an increase in swine flu cases in many parts of the country.

• 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.

• Union Minister for Health and Family Welfare J.P. Nadda reviewed the prevailing situation and preparedness for H1N1 Influenza in the country.

• The minister called for continued strengthening of early detection, timely testing and appropriate clinical management of influenza cases, along with effective utilisation of the existing surveillance and laboratory network.

Four types of influenza viruses

• There are 4 types of influenza viruses, types A, B, C and D. Influenza A and B viruses circulate and cause seasonal epidemics of disease.

i) Influenza A viruses are further classified into subtypes according to the combinations of the proteins on the surface of the virus. Currently circulating in humans are sub-type A(H1N1) and A(H3N2) influenza viruses. The A(H1N1) is also written as A(H1N1)pdm09 as it caused the pandemic in 2009 and replaced the previous A(H1N1) virus which had circulated prior to 2009. Only influenza type A viruses are known to have caused pandemics.

ii) Influenza B viruses are not classified into sub-types but can be broken down into lineages. Influenza type B viruses belong to either B/Yamagata or B/Victoria lineage.

iii) Influenza C virus is detected less frequently and usually causes mild infections, thus does not present public health importance.

iv) Influenza D viruses primarily affect cattle and are not known to infect or cause illness in people.

• A key feature of influenza viruses is their ability to evolve continuously and rapidly.

• An estimated 1 billion cases of influenza occur annually, of which 3-5 million are severe, resulting in between 290,000 and 650,000 influenza-related respiratory deaths.

• Most people recover from fever and other symptoms within a week without requiring medical attention.

• Vaccination is the best way to prevent the disease.

• Immunity from vaccination goes away over time so annual vaccination is recommended to protect against influenza.

• The vaccine may be less effective in older people, but it will make the illness less severe and reduce the chance of complications and death.