The epidemic on the way: Why winter flu is so bad this year

The epidemic on the way: Why winter flu is so bad this year


Cavallini James/BSIP/Science Photo Library By Debora MacKenzie   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 virus, and you get sick again. You still have some immunity to kinds of flu that are only a little different from viruses you have seen before, which is why much winter flu isn’t as severe as flu can be. The strains best able to evade this kind of prior immunity dominate the annual epidemic in each hemisphere, so we only need one vaccine per season – but a new one each year. A record number of flu strains are currently circulating, two in the influenza B group and two influenza A strains,
  • 首页
  • 游艇租赁
  • 电话
  • 关于我们