A person is considered contagious when prodromal symptoms, active sores, and healing lesions are present. Herpes is potentially contagious when no symptoms are present. That is, a person who has genital herpes is potentially always shedding active virus. Lesions can occur deep inside the vagina where they cannot be seen or felt, but can readily transmit the virus. Oral herpes can be transmitted to the genitals, and vice versa.
Symptoms are similar.
Towels are especially conducive to this. It is possible to have more than one primary infection. Environmental surfaces like toilet seats may be a source of contagion, but there is no evidence that this poses a real threat to the general population. Experts differ as to how long the virus can survive on its own. The primary cause of infection remains intimate contact.