Risk of transmission following HIV exposure

Table 1: Exposure and transmission risk/exposure with known HIV-positive source who is NOT on antiretroviral treatment 

Type of exposure with known HIV-positive source who is NOT on antiretroviral treatment Estimated risk of HIV transmission/exposure*
Receptive anal intercourse (RAI)
   - ejaculation
   - withdrawal

Shared needles and other injecting equipment 1/125
Insertive anal intercourse (IAI) uncircumcised  1/160
Receptive anal intercourse (IAI) circumcised 
Receptive vaginal intercourse (RVI)  1/1250
Insertive vaginal intercourse (IVI)  1/2500
Receptive or insertive oral intercourse Unable to estimate risk - extremely low
Needlestick injury (NSI) or other sharps exposure  1/440
Mucous membrane and non-intact skin exposure** <1/1000

Table source: 2016 National guidelines for post-exposure prophylaxis after non-occupational and occupational exposure to HIV (external site).


*These estimates are based on prospective studies, not cross-sectional data or figures derived from modelling. These estimates do not take into account source viral load, which if undetectable markedly reduces risk estimates.
** Human bites are extremely low risk