Most STIs cannot be transmitted through casual contact with people or contaminated objects because they require direct contact with infected bodily fluids, such as blood, semen, vaginal secretions, or breast milk, during sexual activity or through sharing of needles. These infections are not transmitted through casual contact such as hugging, shaking hands, or using the same toilet seat. Additionally, many STIs cannot survive outside the body for very long, which further reduces the risk of transmission through contaminated objects.