Cavallini James/BSIP/Science Photo Library
Why does flu keep coming back?
Flu is unique among human diseases. It circulates constantly in cool, dry areas of east Asia, conditions the virus prefers, but when temperatures drop during the northern and southern winters, it breaks out and begins a tour of the relevant hemisphere. Because it spreads from person to person efficiently in exhaled droplets, and can be picked up from contaminated surfaces, nearly everyone is exposed.
And unlike, say, measles, having flu once doesn’t make you immune to catching it. The virus is uniquely talented at dodging our immune systems. The big haemagglutinin protein on its surface gets most of your immune system’s attention, and this protein constantly mutates at seven hotspots. Every few years it racks up such a number of mutations that many antibodies you made to your last infection don’t recognise the
Published at Wed, 03 Jan 2018 16:00:00 +0000