I will join the answer above, but I also need to note several diseases associated with this transmission mechanism:
Suddenly, you got saliva from a person who is currently sick with Hepatitis A (Botkin's disease) and you did not adhere to the rules hygiene, then there is a very high risk of getting sick, but from this list this disease does not greatly threaten your life, it is easily and without any complications transferred by the body.
Syphilis can also be transmitted through the saliva of a sick person, but only in that case if he has a rash in the mouth or on the lips from which the pathogen (treponema pale) can enter the external environment.
The only thing you can catch is syphilis. With patients with syphilis, or, as they are also called, lepers, you need to exclude any physical contact, not to mention the exchange of body fluids. Although it is not dangerous to talk or just be around a person, the disease is not transmitted by air.
I will quote the phrase of one of my lecturers on infectious diseases: "HIV is secreted by the salivary glands of a person, but if you want to become infected with it, you will have to pour a whole bucket of saliva on yourself"
The maximum concentration of HIV is in semen, vaginal secretions and blood, and the main routes of infection are blood and sexual. If you do not inject with one needle with a homeless person and do not have sex with him, the risk of infection will tend to numbers significantly less than one. The same goes for hepatitis.