Seasonal flu will hit India and the rest of the northern hemisphere hard next year, predict flu-trackers based on outbreak trends in the winter of the southern hemisphere, where Australia has reported record-high numbers of cases, hospitalizations and deaths.
Australia had 233,453 lab-confirmed cases of seasonal flu till mid-November, compared to 87,333 during the same period last year, with hospital admissions up 2.3 times the five year average.
Compounding the longer duration and severity of the outbreak is the worrying news that the vaccine effectiveness against H3N2, which is the predominant influenza strain this winter, is only 10%.
Since several different viruses cause seasonal influenza and these viruses are subject to continual antigenic changes (“antigenic drift”), World Health Organization (WHO) every year recommends a new strain-specific vaccine in February for the northern hemisphere and in September for the south to prevent infection. Each new vaccine targets three to four of the most deadly flu strains causing infection based on flu-tracking data from the previous five to eight months from 143 National Influenza Centres in 113 countries, including India.