不是因为受凉了抵抗力降低。 而是另外有两个原因：

There are two main theories for why cold and flu season peaks in winter:

(1) When a person with a respiratory virus coughs or sneezes, the virus escapes the host via a small droplet. In colder months, the virus can more easily remain in the air to infect another person.

(2) the more people stay indoors or in school, in close contact, the more chances viruses get to spread,