It is extremely unlikely that you will get herpes or AIDS from a hot tub or whirlpool, but you can get herpes from sitting on the side of a pool or folliculitis, a bacterial infection of your skin from a hottub. The herpes and AIDS viruses are killed almost immediately in chlorinated water. As far as we know, the AIDS virus is acquired only from infected blood, semen and other body tissues, but the herpes virus can survive for up to 4.5 hours on plastic coated benches or seats. Even if you sat on the same spot that a person with active herpetic blisters has just left, you probably wouldn't be infected. To acquire herpes, you need to allow the virus to pass through broken skin.
Herpes often occurs on the genitals because lovemaking can break the skin to let the virus in.
Sitting on a toilet seat that has herpes virus on it with broken skin on your buttocks can cause a recurrent herpes infection on the buttocks. Hot tubs that have not been adequately chlorinated can give you folliculitis, a condition that causes severe itching and red bumps on the skin. It can be cured with antibiotics, but often goes away by itself without treatment. If you start to itch, check with your doctor. I'm Dr. Gabe Mirkin on Fitness.