Why do some people have a fever after burning paper in Tomb-Sweeping Day? Is it because of the heavy yin?

Superstition is that the dead relatives will go home, follow you and pester you to go home to visit relatives, so they will feel sick and have a fever.

Scientifically speaking, it is clear and humid, and the cemetery is even more humid and cold. After burning paper to worship, there is fire, and people themselves are contaminated with moisture, and the paper is barbecued, which leads to poor physical fitness, colds and fever.