It begins as surely as the leaves dropping off the trees. As the mercury drops and the sunlight fades, the sniffles set in. At best, it’s just a cold that leaves us with the strange feeling that we’ve swallowed a cheese grater; if we’re unlucky, our body is wracked with a high fever and aching limbs for up a week or longer. We have flu.
The flu season arrives so predictably, and affects so many of us, that it’s hard to believe that scientists have had very little idea why cold weather helps germs to spread. Over the last five years, however, they have finally come up with an answer that might just offer a way to stem the tide of infection – and it revolves around a rather grim fact about the ways that your sneezes linger in the air.
A new understanding of influenza couldn’t come quickly enough; worldwide, up to five million people catch the illness each flu season, and around a quarter of a million die from it. Part of its potency comes from the fact that the virus changes so quickly that the body is rarely prepared for the next season’s strain.
“The antibodies we’ve built up no longer recognise the virus – so we lose our immunity,” says Jane Metz at the University of Bristol. It also makes it harder to develop effective vaccines, and although you can engineer a new jab for each strain, governments often fail to persuade enough people to take it up.
The hope is that by understanding better why flu spreads in winter, but naturally fades in summer, doctors could find simple measures to stop its spread. Previous theories had centred on our behaviour. We spend more time indoors in the winter, meaning that we’re in closer contact with other people who may be carrying germs.
We’re more likely to take public transport, for instance – and as we’re pressed against spluttering commuters, misting up the windows with their coughs and sneezes, it’s easy to see how this could send us over a tipping point that allows flu to spread through a population.
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