Assortment of five respiratory viruses triggering infection now

Assortment of five respiratory viruses triggering infection now

HYDERABAD: It’s not one, but an assortment of at least five respiratory viruses has been dominating the infection scenario over the last five months, causing mild to severe illness.

Doctors began witnessing unusual cases of fever, cough and cold, different from Covid-19, in September 2022, but most went undiagnosed then. Now, official data shows it was a bouquet of respiratory viruses, including swine flu that caused hospitalisation and deaths.

Official data shows apart from the Covid-19 virus, swine flu (H1N1) that caused the 2009 pandemic, H3N2 of 1968 Hong Kong flu notoriety, and the seasonal Victoria and Yamagata lineages of influenza B viruses are in circulation, with each of these viruses dominating infection charts at one point in time.

Health experts don’t rule out presence of H3N2v, a descendant of the 2009 pandemic swine flu, as human-to-human transmission has been reported from some parts of the world, including the US. Official data, however, is silent on H3N2v strain.

While Covid-19 was nearly obliterated from the infection scenario for certain periods, the long-forgotten swine flu unwittingly filled the gap by infecting more people. Even the Victoria lineage led the infection charts for several weeks.

But, as the focus was more on Covid-19, these respiratory viruses, which are equally severe in nature, went unreported.

Though influenza A strain H3N2 is currently dominating the infection charts, its sister influenza B lineage Victoria is also in circulation in significant numbers since January. Originally a milder lineage, influenza B has of late acquired severity and causing hospitalisations, doctors warn.

Weekly data from Indian Council of Medical Research (ICMR) reveals that H3N2 has of late taken the lead pushing Covid-19 aside. Latest official statistics reveal of the samples tested for the week (March 5 – 11), 37 are of H3N2, 10 of Victoria, eight of Covid-19 and one of swine flu.

Before H3N2 became dominant since January 1 this year, swine flu was the leading cause of respiratory infections between April 18, 2022 and December 31, 2022.

H3N2 was, however, present all through the year of 2022, but lying low with fewer infections. The Covid-19 was dominant from December 27, 2021 to February 27, 2022, peaking in mid-January 2022.

The Victoria lineage caused more infections between August 16, 2021 and January 2, 2022 with the cases peaking in September 2021.

Though non-Covid-19 respiratory viruses got attention early this month with rising cases of cough and cold, right from September 2022 several doctors posted on CME India, a continuing medical education online portal, that they had been seeing patients with viral pneumonia.

But they could not diagnose the cause. They had described it as a flu far more dangerous than Covid-19.One of the physicians, Dr Ravi Premchand, said he had seen 10 such cases with two fatalities in one month.