New flu virus mutation could see 'worst season in a decade'

"Flu strikes every winter, but this year something seems to be different. A seasonal flu virus suddenly mutated in the summer. It appears to evade some of our immunity, has kick-started a flu season more than a month early, and is a type of flu that history suggests is more severe. The NHS has now issued a "flu jab SOS" as fears grow that this will add up to a brutal winter. There is a lot of nuance and uncertainty, but leading flu experts have told me they would not be shocked if this was the worst flu season for a decade."

"Scientists track the evolution of influenza viruses because they mutate constantly and the seasonal flu vaccine has to be updated each year to keep up. This evolution happens in a rhythm known as "shift and drift". Most of the time the virus drifts along making minor changes and then every so often there is a sudden abrupt shift as the virus mutates substantially. That happened in June this year. Seven mutations appeared in a strain of H3N2 seasonal flu and led to a "fast increase" in reports of the mutated virus, says Prof Derek Smith, director of the centre for pathogen evolution at the University of Cambridge."

A seasonal H3N2 influenza virus acquired seven mutations in June, producing antigenic changes that partly evade existing population immunity. The mutation emerged unusually in the northern hemisphere summer and spread rapidly, causing a fast increase in reports. By September, as children returned to school and temperatures dropped, cases rose and the flu season began more than a month early. H3N2 is historically associated with more severe illness. Health services have issued urgent calls to increase flu vaccination uptake to reduce pressure on healthcare systems. Continued surveillance and vaccination efforts aim to mitigate the season's impact.

Read at www.bbc.com