risk of HIV transmission by exposure type

Last edited 03/2018

transmission risk by exposure type

The risk of HIV transmission depends on the exposure and degree of viraemia of the source.

• needlestick injuries
• occurs following a needlestick injury with a needle contaminated with blood from a source known to have HIV
• in healthcare setting source patient (serology) known
• risk of becoming infected with HIV is thought to be between 0.1% and 0.36%
• increased risk if large gauge needle, hollow needle, deep injury, visible blood on the device, needle was in patient "s artery/vein, or if the source patient has AIDS (or terminal illness).


• in healthcare setting source patient unknown or unable to test source
• risk assessment required of the type of injury and the likely infection status of the source
  
  
• community needle stick
• risk is more difficult to estimate and the exact incidence of needlestick injuries and the transmission rate is unknown
• overall low risk and requires a risk assessment of the type of injury, location of the discarded needle (for example if discarded in a location where people who inject drugs are known to inject), likely age of the discarded needle and the background prevalence of HIV in the local population
  
  
• post-exposure prophylaxis (PEP) is thought to reduce seroconversion by up to 81%
  
  
• mucous membrane and non-intact skin exposure to blood - the risk is very low
• risk for transmission of HIV via mucous membrane exposure is estimated to be 0.09%
  
  
• intact skin exposure to blood - no risk
  
  
• human bites
• very low risk
• risk assessment required
• only risk if blood in the mouth of the biter, and significant injury. No risk if no blood in mouth of biter, and exposure to saliva only
• if source co-infected with HCV, HCV transmission more likely than HIV transmission
  
  
• sexual exposure
• risk of transmission of HIV following sexual exposure depends on
• the type of exposure
• the viral load of the source the susceptibility of the host
• the presence of sexually transmitted infections in either the source or the recipient
• if the index partner also has a genitourinary infection, for instance, the risk of transmission is approximately doubled.
• if the recipient has a genitourinary infection, the risk of acquiring HIV is also elevated
  
  
• heterosexual exposure (general)
• if source on antiretroviral therapy with suppressed viral load transmission rate = 0 (if viral load < 400 copies/ml)
• increased risk if source patient has recently seroconverted, e.g. within 2.5 months of seroconversion risk of transmission is estimated to be 0.0082/coital act
  
  
• receptive vaginal intercourse
• overall risk is 1 in 1000, which is increased in the presence of cervical ectopy, genital tract trauma, menstruation, genital ulcerative disease (in either partner), infectious syphilis and pregnancy
• male circumcision reduces HIV acquisition
  
  
• insertive vaginal intercourse
• overall risk is 1 in 1219
  
  
• men who have sex with men (MSM) unprotected receptive anal intercourse
• overall risk is 1 in 90
• increased risk if there is ejaculation within the rectum.
• the PARTNER study has demonstrated zero transmissions in HIV serodiscordant couples where the HIV positive individual is on effective antiretroviral therapy
  
  
• MSM unprotected insertive anal intercourse
• overall risk is 1 in 666
• the PARTNER study has demonstrated zero transmissions in HIV serodiscordant couples where the HIV positive individual is on effective antiretroviral therapy
  
  
• orogenital contact
• overall very low risk, estimated to be <1 in 10,000 for both receptive and insertive oral sex

Reference:

• (1) Health Protection Surveillance Centre (HPSC) 2016. Guidelines for the Emergency Management of Injuries and Post-Exposure Prophylaxis (PEP)