It’s that time of the year again. You probably think I mean Christmas, but as a virologist the sight of glitter, fairy lights and moulting pine trees immediately makes me think of the flu season. And if there’s one thing that can ruin your family’s Christmas, it’s the arrival of that particular unwanted guest.
Most years you’d be rather unlucky if the real flu gate-crashed your Christmas party since, despite the rising tide of sneezes, coughs and sniffs heard in the streets of Europe and North America since October, these are usually just the minor respiratory viruses – mere heralds of the big one still to come. Influenza A (and its frequent companion influenza B) usually times its major arrival for early in the new year.
Getting the big picture
The World Health Organisation (WHO) monitors global flu patterns by collating the results of tests for flu performed in hospital labs around the world. Of course, only a small minority of those of us who catch the flu will be ill enough to warrant a diagnostic test, but this sample is enough to generate an idea of the bigger picture.
India had an alarming encounter with influenza A subtype H1N1, the descendent of the 2009 “swine flu” pandemic, at the tail end of the last flu season. A death rate of about 6% (from over 30,000 cases) suggests a virus that, while not alarmingly contagious, was nevertheless very nasty. Fortunately, this bad experience in India was not carried over into the southern hemisphere flu season in mid-2015 (since Australia is upside down, their flu season also happens upside down, during the northern hemisphere summer) where the majority of flu cases have been influenza B type, and significantly milder.
As of the date of the last WHO snapshot, November 26 2015, the tail end of the Australian flu season is now definitely over.
The flu is once again on the march north and west, but its presence is only really being felt in a belt from the Middle East to South-East Asia, where the predominant form is currently H1N1. At the western end of that belt, a small percentage of influenza B is in the mix and toward the eastern end, subtype H3N2 – a far older adversary that has been circulating almost every year since 1968. In Europe itself, the overall level remains low, but the tests that have been performed indicate mostly H1N1 in the north and a three-way split between H1N1, H3N2 and influenza B in more southern parts.
There’s fortunately no indication of any Indian-style increases in virulence, and unlike last year no worries as yet that the vaccine may be inadequate.