There is a myth in the Bikram and Hot Yoga world:
If you are sick, you can’t possibly spread germs in the hot yoga room because bacteria and viruses “can’t survive in the hot room”.
There is no evidence to support this assertion.
If the yoga room was hot enough to kill a virus, it would probably be hot enough to kill YOU.
As an example, the Influenza virus can be killed by heat AT TEMPERATURES ABOVE 166°F [75°C].
A Bikram Yoga hot room is around 105°F [40°C]. It’s not hot enough to kill the flu virus.
You might hear the argument that “your body creates a fever to kill viruses and bacteria”, so naturally a hot yoga room must have the same benefit.
This is only true to a point. A fever is not the only weapon your body has, and a fever alone doesn’t knock out microbes: your immune response is more complicated than that, and includes specialized cells that act as defenders against invaders.
When your internal (core) temperature rises, that is a fever. In an adult, a fever up to about 103°F [39.4°C] is not usually dangerous, but go higher than that and you risk serious health effects, up to and including brain damage. If the yoga room was hot enough to raise core temperature, it would be a very dangerous place to spend 90 minutes.
Most Hot Yoga practitioners and teachers will argue that the temperature of the room is a safe range. Your body regulates your internal temperature through sweat and blood circulation, to keep you around 98°F[37°C]. If your internal (core) temperature rises above safe levels in response to external temperatures, you face heat exhaustion or heat stroke. If you could raise your core temperature to “fever” levels by just being in the yoga room for a while, you’d have a very bad time.
Either the hot room is a safe enough temperature for you to spend 90 minutes, or it’s hot enough to kill microbes. It can’t be both.