Slight change in H1N1 virus behind rise in cases: Experts

A slight change in the pandemic H1N1 virus (swine flu) could be the reason for the rise in cases and deaths in several southern states since January this year, experts of the National Institute of Virology (NIV) said.

The NIV, which calls this change an “antigenic drift”, has said the current vaccine will now only partially protect patients. NIV has ruled out any major mutation of the virus and said that the antigenic drift is likely to have led to local outbreaks.

From January till mid-march this year, there have been reportedly over 5,000 cases and more than 125 deaths across the country. The western and southern states have been largely affected.

Maharashtra has the highest number of 63 deaths and 298 cases. This prompted state Health Minister Dr Deepak Sawant to call a review meeting at Pune on Monday. Pune figures high on the list with 27 deaths followed by Nashik at 11.

Influenza virus positivity among patients was nearly 25 per cent in the southern states of Tamil Nadu, Kerala, Andhra Pradesh and Telangana, Dr Soumya Swaminathan, Director General of Indian Council of Medical Research told The Indian Express.

Till mid-march, there were more than 3,000 cases in Tamil Nadu and Telangana. While Telangana recorded 16 deaths, the toll was 13 in Andhra Pradesh, 7 each in Karnataka and Kerala and 10 in Tamil Nadu.

Fewer number of cases have been reported in northern states although according to Swaminathan, the H1N1 virus peaks during the winter months here.

In the past eight years, flu shots around the world contained a virus that was retrieved from a sick person in California in 2009 - (early days of H1N1 ) However, in September last year, the World Health Organisation recommended changing the 2009 H1N1 component for the southern Hemisphere’s 2017 flu vaccine.

This is the first change in the H1N1 component since the former pandemic virus became a globally circulating seasonal flu strain, said Swaminathan.

Referring to the “antigenic drift”, Dr M S Chadda, Deputy Director, NIV, told The Indian Express, “Thesearesmallchanges in the genes of influenza viruses that happen over time as the virus replicates. These small changes usually produce viruses that are closely related to one another. The present vaccine has performed strongly against the H1N1 component. But it will now only partially protect against the virus.”

The newly-recommended H1N1 vaccine strain called A/michigan/45/2015 now replaces the longstanding A/california/7/ 2009 one and is recommended to improve protection against two subclades that have emerged over the past season, experts have said.

The new vaccine will be available only by May, the state health minister told The Indian Express.

Pune records 27 deaths followed by Nashik at 11.