Did Covid-19 lead to extinction of Influenza B virus?
There has been a notable reduction in influenza cases since the SARS-CoV-2 pandemic.
While coronavirus has emerged as the worst havoc in modern times, the pandemic may have silently led to the extinction of an influenza virus, which has been a seasonal epidemic in several parts of the world.
There has been a notable reduction in influenza cases since the SARS-CoV-2 pandemic. One particular flu viral infection agent, the B/Yamagata lineage of Influenza B virus, was not detected from April 2020 to August 2021.
According to a research paper published in Nature Reviews microbiology, the developments suggest that influenza lineage may have become extinct, which may provide opportunities for improving the availability and effectiveness of influenza vaccines.
Reportedly, detection of Influenza virus cases dropped significantly from April 2020 with a "99 per cent reduction compared with previous years despite roughly similar levels of testing."
"The genetic diversity of influenza viruses has also dramatically diminished. The number of cases detected has fallen for both influenza A (H3N2) and A (H1N1) subtypes, and, similarly, diversity has diminished for the B/Victoria lineage," the paper stated. The paper, however, also noted that the IBV lineages have been known to periodically enter a state of "dormancy" for long time intervals. Influenza B was mostly undetected globally during the 1990s, except for an outbreak in Asia.
WHAT IS THE INFLUENZA VIRUS?
Influenza is a group of viruses that leads to contagious respiratory illness infecting the nose, throat, and at times lungs. There are four types of seasonal influenza viruses, types A, B, C and D. Influenza A viruses are further classified into subtype A (H1N1) and A (H3N2).
According to the World Health Organisation (WHO), Influenza B viruses are not classified into subtypes but can be broken down into lineages. Currently circulating influenza type B viruses belong to either B/Yamagata or B/Victoria lineage.
The initial symptoms of Influenza include sudden onset of fever, cough, headache, muscle and joint pain, sore throat and a runny nose. While most people recover in a couple of weeks, severe cases may lead to death.
WHAT COULD HAVE TRIGGERED A REDUCTION IN CASES?
Researchers have said that the global circulation patterns of influenza viruses have been associated with age-specific patterns of infection. Pregnant women, children under 59 months, the elderly, individuals with chronic medical conditions are at a higher risk of being affected by the virus.
Led by Marios Koutsakos of the Department of Microbiology and Immunology, University of Melbourne, the researchers speculate that behavioural changes (social distancing, mask-wearing and hygiene measures), travel and movement restrictions could be the major factors driving the reduction in influenza incidence.
"The reduction in global movement due to the Covid-19 pandemic may have contributed to low distribution and seeding of B/Yamagata and with B/Victoria prevalence increasing since 2019, B/Yamagata may have already been at a low prevalence cycle at the beginning of the pandemic," the paper added.
Meanwhile, the reduction in cases could bode well for the health sector, which now has more vaccines to fight fewer strains of the virus and work on improving the effectiveness of the doses in fighting those remaining strains.