HIV is contained in the human body in so-called body fluids. The concentration of the virus depends on the type of such fluid.
Higher concentrations of HIV are observed in:
Lower concentrations of HIV are observed in*:
*if they do not show visible amounts of blood
The ways HIV can be transmitted:
Blood to blood
Reuse of the equipment for injections, piercing, tattooing (i.e., needles/syringes), or any other direct contact with the blood of a person infected with HIV
Mother to child
During pregnancy, childbirth, and breastfeeding if preventive measures are not taken
Sexual intercourse without a condom
Anal, vaginal, and oral
So, only four body fluids contain a sufficient amount of the virus for a person to get infected, and in particular, blood, semen, vaginal fluid, and breast milk. All other biological fluids are completely safe unless they contain visible amounts of blood.
HIV cannot be transmitted through:
Insects (mosquitoes, bedbugs, lice, etc.)
Everyday items (dishes, clothing, telephone, and toilet seat)
Coughing and sneezing
Factors that increase the chances of getting infected:
The presence of other STIs that make a human body more vulnerable to infection
A high concentration of the virus in the blood of an HIV-positive person (e.g., HIV+ people who regularly use antiretroviral therapy have significantly lower concentrations of the virus in their body than HIV-positive people who do not use the mentioned therapy).
It requires the following to get infected:
The virus must be present in a body fluid
The number of copies of the virus carried in a body must be sufficient