A Systematic Review of Risk of HIV Transmission Through Biting or Spitting

Implications for Policy

FV Cresswell; J Ellis; J Hartley; CA Sabin; C Orkin; DR Churchill


HIV Medicine. 2018;19(8):532-540. 

In This Article

Abstract and Introduction


Objectives: The perceived threat of HIV transmission through spitting and biting is evidenced by the increasing use of "spit hoods" by Police Forces in the UK. In addition, a draft parliamentary bill has called for increased penalties for assaults on emergency workers, citing the risk of communicable disease transmission as one justification. We aimed to review literature relating to the risk of HIV transmission through biting or spitting.

Methods: A systematic literature search was conducted using Medline, Embase and Northern Lights databases and conference websites using search terms relating to HIV, AIDS, bite, spit and saliva. Inclusion and exclusion criteria were applied to identified citations. We classified plausibility of HIV transmission as low, medium, high or confirmed based on pre-specified criteria.

Results: A total of 742 abstracts were reviewed, yielding 32 articles for full-text review and 13 case reports/series after inclusion and exclusion criteria had been applied. There were no reported cases of HIV transmission related to spitting and nine cases identified following a bite, in which the majority occurred between family (six of nine), in fights involving serious wounds (three of nine), or to untrained first-aiders placing fingers in the mouth of someone having a seizure (two of nine). Only four cases were classified as highly plausible or confirmed transmission. None related to emergency workers and none were in the UK.

Conclusions: There is no risk of transmitting HIV through spitting, and the risk through biting is negligible. Post-exposure prophylaxis is not indicated after a bite in all but exceptional circumstances. Policies to protect emergency workers should be developed with this evidence in mind.


Detailed epidemiological studies since the 1990s have provided insight into the risk of HIV transmission through sexual exposure and needlestick injuries, and have informed policy and behaviour around the use of barrier contraception, universal precautions and HIV post-exposure prophylaxis (PEP).[1–8] Recent longitudinal studies have also shown that HIV-positive individuals on antiretroviral therapy (ART) with an undetectable plasma HIV viral load do not transmit HIV and there is increasing acceptance of the concept "undetectable = untransmissible" (U=U).[9,10] National guidelines on HIV PEP have used these data in informing their recommendations. Provision of PEP is not recommended following potential exposure from biting and spitting; however, the risk of HIV transmission from such exposures has not been systematically evaluated.[11]

In the UK, human bite injuries are a common presentation to the emergency department, comprising around 0.1% of all attendances.[12] Bites represent an occupational risk to emergency workers such as policemen, paramedics, doctors and nurses, and are more likely to occur when dealing with patients with seizures, aggressive members of the public, children and those with cognitive impairment.[13] In the USA there are an estimated 622 bites to emergency workers per year.[14] A retrospective 4-year review of attendees to a single UK emergency department identified 421 presentations with human bites, amounting to one every 3 days.[12] Bites vary in severity from petechial haemorrhage to contusion, abrasion, laceration and avulsion.[15]

Spitting represents another occupational hazard faced by emergency workers, with the Metropolitan Police alone reporting 264 spitting incidents between 2014 and 2016.[16] Saliva has been shown to lyse HIV particles in vitro as a result of hypotonicity and many salivary proteins inhibit and inactivate HIV particles.[17]

The perceived threat of HIV and other blood-borne virus transmission through spitting and biting is evidenced by the increasing use by police forces of "spit hoods" (which are placed on potential assailants to reduce the risk of exposure to arresting officers). As of November 2016, 17 out of 49 police forces in the UK now use "spit hoods".[18] In addition, a draft parliamentary bill has called for increased penalties for assaults on emergency workers, citing the risk of communicable disease transmission as one justification.[19] The draft bill also recommends mandatory provision of "intimate samples, without reasonable excuse" from those accused of spitting on emergency workers, with refusal to provide such specimens punishable as an offence. In the USA, harsh sentencing for those accused of spitting while knowingly HIV positive has been carried out, with the accused charged with causing harm by "means of a deadly weapon".[20]

We undertook a systematic literature review of HIV transmission related to biting or spitting to ensure that decisions about future policy and practice pertaining to biting and spitting incidents are informed by current medical evidence.