Factors that affect a person's risk of contracting human immunodeficiency virus include having unprotected sex, sharing needles with infected individuals and using tattoo needles without sterilizing them, reports WebMD. Circumcision and having other sexually transmitted infection may also affect a person's risk of contracting HIV.
Since human immunodeficiency virus can spread through semen and vaginal secretions, having unprotected vaginal, anal or oral sex without knowing a partner's HIV status may increase the chances of contracting the virus, explains WebMD. Having sex with several partners may also increase a person's chance of contracting HIV.
Individuals who use intravenous drugs as well as those who share equipment used to prepare or inject such drugs, such as needles and syringes, are at a higher risk of contracting the HIV virus, according to WebMD. Using contaminated needles for tattooing and piercing without sterilizing them may also affect a person's risk of contracting the virus.
Male circumcision may affect HIV transmission risks, according to the Centers for Disease Control and Prevention. Studies show that uncircumcised males face a higher risk of transmission of HIV with heterosexual activity, reports Mayo Clinic.
Having another sexually transmitted disease may also affect a person's risk of contracting the virus, according to Mayo Clinic. This is because certain sexually transmitted infections leave open sores on a person's genitals, which make it easier to contract HIV.