Risk of HIV transmission by exposure type

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)