Now we know why flu is worse in winter, why more people are more likely to get sick, and what we can do about it…

Yale researchers have pinpointed a key reason why people are more likely to get flu during winter months – low humidity (dry air).

Led by Akiko Iwasaki, the Waldemar Von Zedtwitz Professor of Immunobiology, the research team explored the question using mice genetically modified to resist viral infection as humans do.

The mice were all housed in chambers at the same temperature, but with either low or normal humidity. They were then exposed to the influenza A virus.

Low humidity hinders immune response

The researchers found that low humidity hindered the immune response of the animals in three ways:

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  1. It prevented cilia, which are hair-like structures in airways cells, from removing viral particles and mucus.
  2. It also reduced the ability of airway cells to repair damage caused by the virus in the lungs.
  3. The third mechanism involved interferons, or signalling proteins released by virus-infected cells to alert neighbouring cells to the viral threat. In the low-humidity environment, this innate immune defence system failed.

The study offers insight into why the flu is more prevalent when the air is dry.

“It’s well known that where humidity drops, a spike in flu incidence and mortality occurs. If our findings in mice hold up in humans, our study provides a possible mechanism underlying this seasonal nature of flu disease,” says Iwasaki.

5 Flu facts you need to know

Easy flu fighter

According to the researchers, increasing water vapour in the air with humidifiers at home, school, work, and even hospital environments is a potential strategy to reduce flu symptoms and speed recovery.

Source: Yale University via www.sciencedaily.com

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