It’s getting colder outside, and you know what that means—it’s time for flu season. Why do people get more colds, flu and now COVID-19 when it’s very cold outside?

In a new study, scientists have found the answer. It ________ that the cold air itself damages (破坏) the immune response (免疫反应) in our noses.

The nose is an important part of our body’s immune system. When a virus goes into the nose, the nose finds it, and the cells (细胞) there begin to ________ billions of simple copies of themselves called extracellular vesicles (EVs).

“EVs can’t divide like cells can, but they are like little mini versions of cells ________ can kill the viruses,” Benjamin Bleier, the author of the study from Harvard Medical School, told CBS News. “They are like little arms that grab on to the viruses as you breathe them in.” Then, the viruses sticking to EVs will got out from our body in the ________ of snot (鼻涕).

However, when cold weather hits, the nose’s “superpower” becomes ________ powerful. The study found that when the temperature inside the nose drops by 5°C, nearly 50 percent of the billions of EVs will be taken out of the ________. “Cold air makes people catch viruses more easily because you have lost half of your immunity”, said Bleier.

This is ________ we should wear masks in winter. “Wearing masks can not only ________ us from viruses, but it’s also like wearing a sweater on our nose.” Bleier said. The warmer you keep your nose, the better it works to fight against viruses.

In the future, Bleier expects to see the ________ of medicine that build upon this new finding. Scientists may find a way to “fool the nose into ________ it has just seen a virus”, Bleier said.