Why is the incidence of fever or other diseases higher at night?

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Not only fever, but other physical ailments and their discomfort are more prevalent at night. If my husband ever has a fever or a sore throat, he is fine all day long, but if he stays up a little longer at night, his incidence gradually increases.
We all know that viruses cannot be effective at high temperatures. The virus becomes active in the body in any physical illness. They need temperature to destroy. Due to the high temperature during the day, the body does not need to raise the temperature separately. Our immunity is also more effective during the day which keeps us safe. At night, the ambient temperature is low and the body's immune system is less effective, so the infection spreads faster. As a result, to destroy those viruses, the body has to be heated separately to deal with them, due to which the body temperature is felt to be high. As well as waking up in the morning, the body's immune system is ready to deal with all the adverse situations and illnesses. The brain also helps the immune system to be active in other functions. This is why in the morning we can feel the improvement in physical condition.