Herpes is a sexually transmitted disease spread through saliva. According to WebMD, Hepatitis B can be transmitted by sharing a toothbrush with someone who has it.
The germs that cause viral STDs hide in blood, vaginal secretions, semen and only sometimes in saliva. The herpes simplex virus passes through saliva to the uninfected person by getting into contact with the skin or mucous membranes. The risk of infection is higher with direct contact from sores or blisters during an outbreak. HIV is not transmitted through saliva, but it may be transmitted by coming in contact with blood from sores or bleeding gums.