Road accidents

Only one case has been reported where a blood spillage during a road accident was the source of infection (Hill). Fears about this eventuality need to be considered not only in the context of the likelihood of coming into contact with an HIV-positive person in this situation, but also the small risk of transmission from blood splashes, as established from the follow–up of health care workers exposed to blood. See Transmission to health care workers earlier in his chapter.

Traumatic accidents in sport

Only one case has been reported where a man was seemingly infected by another man as a result of bashing his head against another man's head during a football match (Torre). Blood was seemingly exchanged, but we cannot be certain that the man who believed he had been infected was uninfected beforehand, despite his failure to report any risk factors. Much greater risks in sport already exist, notably penetrative sex between men and the sharing of needles to inject steroids.

Contaminated blood transfusion getting through the screening system

Only two cases have been reported in the UK where HIV transmission has occurred after a blood transfusion, presumed to be negative, has been given to a patient. In both cases the blood came from the same source. This should be seen in the context of only 190 blood donations identified as HIV–positive out of 14.85 million donations during the period between the beginning of screening in 1985 and March 1991.

As long as the epidemic remains concentrated within certain core groups, it appears that the other safeguard in the blood screening system, asking people not to give blood if they perceive themselves to have been at risk, is working successfully despite early criticisms that it would not protect the blood supply.

A healthcare worker infecting patients through invasive surgical procedures

Various estimates have been produced of the risk of HIV transmission during an operation. They speculate on a wide range of levels of risk, leading to confusion.

The chances of a patient seroconverting after a one–hour operation performed by a known HIV–1 positive surgeon were estimated in 1991 to be between 1 in 28,000 and 1 in 500,000 (Lowenfels).

The US Centers for Disease Control (CDC) estimated in 1991 a risk of transmission during any invasive procedure by an HIV–positive surgeon of between 1 in 41,667 and 1 in 416,667. They also estimated that, assuming that a surgeon performs 500 procedures per year and that a surgeon's working lifetime after the acquisition of HIV infection was seven years, the risk of HIV transmission to a patient during this period ranged from 8.1% to 0.8%. They calculated that between 13 and 128 patients could have been infected during invasive procedures performed by HIV infected surgeons in the United States between 1981 and 1990 (CDC).

However, the only case yet identified is that of the Florida dentist, see above.

Biting

Several cases of HIV transmission have been attributed to biting. In one case a five year-old child infected with HIV by transfusion bit his eight year-old brother (Wahn). Infection was not detected until his death from AIDS three and a half years later. His brother was discovered to be HIV–positive. There appeared to be no other explanation for infection: the brother had not received blood and had not been sexually abused to the knowledge of his parents, but his mother had noticed a bite mark on his arm about six months before the younger child died.

In another case a man in the late stages of AIDS suffered a seizure and bit the finger of a neighbour who came to his aid. HIV antibody and antigen tests taken on the day of the incident were negative, but the man tested positive less than two months later. It is believed that the man with AIDS bit his tongue before biting his neighbour, and that blood was therefore present in his saliva (Widmar).

A third case is still under investigation. A man in Florida is believed to have been infected through multiple bites from a woman with bleeding gums. The US Centers for Disease Control have confirmed that they believe this case to be a case of blood to blood transmission, but no full report of their investigation has yet been published.

A fourth case is thought to be the first unequivocal case of HIV being spread by a human bite. The case involved a 31 year-old HIV-positive man who bit his 59 year old mother on the hand during a seizure. The man, who had been previously unaware of his HIV status, was subsequently diagnosed with neurotoxoplamosis. Blood was present in the source patient's mouth since he had bitten his tongue and his mother's hand required stitching when she was taken to hospital.

Twenty-seven days following the incident the woman presented with fever and HIV antibody tests at that time were negative. Thirteen days later (40 days following the exposure incident) she was again tested for HIV infection by two ELISA (enzyme linked immunosorbent assay) tests, and a Western Blot test. The double ELISA testing strategy involved one sensitive and one less sensitive test and was deployed to detect recent HIV infection.

The less sensitive ELISA produced a negative result whilst the sensitive 'detuned' assay was found to be positive and this confirmed recent infection.

Researchers were also able to confirm epidemiological relatedness of the viruses infecting the individuals involved in the accident.

The authors commented "Although the possibility of transmission by human bite seems to be negligible because of the number of infecting particles and the inhibitors in saliva, cases with blood in the biter's mouth may deserve special attention".

In hospital environments, especially where healthcare workers are managing psychiatric, neurological, paediatric or combative patients this sort of exposure could be minimised by the use of gloves or arm protection.

A follow–up of thirty health care workers who cared for a patient with AIDS who bit them showed no cases of seroconversion (Tsoukas).

Fighting

Two cases of HIV transmission have been attributed to blood-to-blood contact as a result of fighting. Both these cases are open to question however.

The Queerbasher: A 49 year-old man tested HIV–positive after a `routine' insurance screening. He was married but claimed to have been impotent for ten years and never to have had sex with another man. He admitted using intravenous drugs on one occasion but was adamant that he had used a clean needle. Following the suggestion of the doctor that he had indeed contracted HIV from needle use, the man enquired whether cuts on the hands might be a route for transmission. He said that at one time he had frequented gay cruising areas with work colleagues with the intention of beating up gay men. He had frequently sustained small lacerations on his hands, and got large amounts of his victim's blood on himself. Doctors noticed recently scabbed lacerations on his hands said to result from a recent fight (Carson).

It is not unusual for men who seek anonymous sex in cruising areas to be the same men who then beat up their sexual partners. Might the man have been lying about his sexual risk factors? We do not know because this line of questioning evidently was not pursued by the authors of this report.

The wedding brawl: A case was reported where a man was diagnosed HIV–positive following a blood donation. His only risk was identified as a fight with a man at a wedding party who was HIV–positive (O'Farrell). This case is an example of a combination approach to providing a case history, since the authors provided not only self–reported evidence, but also data from blood samples taken when the man was hospitalised for an unexplained viral syndrome approximately ten days after the fight. The blood samples taken during his hospital stay were subsequently tested for HIV, and seroconversion was shown to have occurred approximately two weeks after the onset of the illness.

However, these data do not prove that the wedding brawl was indeed the source of infection, although the timing is highly suggestive. It would be necessary to compare HIV sequences from the infected man and the intruder at the wedding.

Fighting between children

A case has been reported of a child contracting HIV from another child living in the same house and frequently sharing the same bed. The index case has a AZT–resistant strain of HIV which has subsequently been isolated in the infected child.

The children were both born to HIV–positive mothers. Child 1 was discovered to be HIV–positive and was diagnosed with AIDS at the age of eighteen months, but Child 2 was repeatedly found to be HIV-negative until acute lymphadenopathy was diagnosed. At this point sequences of HIV from Child 2 were compared with sequences from its mothers and from local HIV-positive control children. Sequences of HIV showed very strong similarities between Child 1 and Child 2, but much greater divergence when compared to the mother of Child 2 or other HIV–positive children, suggesting that Child 1 was the source of infection.

How is infection thought to have happened? Although no exposure of Child 2 to blood or body fluids of Child 1 was witnessed, there were numerous opportunities for exposure. Child 2 had an almost constant rash which was weeping or even bleeding as a result of scratching, whilst Child 1 had frequent nosebleeds and bleeding gums. Child 2 was bitten on more than one occasion by Child 1, as well as being hit so badly that he or she required stitches in the wound (Fitzgibbon). All these circumstances suggest that infection occurred as a consequence of Child 1's blood coming into contact with wounds or damaged skin on Child 2's body.

Infection through contact with faeces

Child infected through household contact with mother

One case has been reported in which a child appears to have been infected through contact with his mother's ulcerated skin. The child had weeping skin rashes too, and it is speculated that the child may have contracted HIV as a result of close contact with his mother (MMWR Report).

Sharing razors, injecting equipment or unsafe sex

A final example should serve as a caution when examining unusual modes of transmission. A young man (Brother 1) who tested negative for HIV antibodies in 1989 and subsequently received only heat treated high purity Factor VIII had seroconverted by January 1992. His CD4 count had declined from 1,102 to 846/500 between 1985 and 1987, and had declined to 120–70 in 1992.

His brother (Brother 2) had tested positive for HIV antibodies in 1985, and had reported a possible seroconversion illness in 1983. His CD4 count ranged from 400 to 550 cells/mm³ between 1987 and 1991 to 110 cells/mm³ in 1992.

Nucleotide sequencing as used in the case of the two children discussed under Fighting between children above showed a strong similarity between viral isolates of Brother 1 and Brother 2. This finding suggests that the virus was transmitted from one to the other. If both brothers had been infected through Factor VIII infusions, researchers would expect to see significant differences in the virus strains carried by the two brothers. This evidence suggests that the brother who had seroconverted by 1992 had not been suffering from a long period of `silent' infection.

Information on the route of transmission relies on self–report; the only means of transmission is said to be the sharing of a razor in 1988, over a year before the last negative test of Brother 2. Brother 2 was transfused with six units of red blood cells from seronegative donors during 1989 and 1990.

Discussion following the presentation of this report at the December 1993 First National Conference on Human Retroviruses and Related Infections centred on the possibility that the brothers had shared injecting equipment in order to self–administer Factor VIII.

The journal report evades the question of whether the virus might have been transmitted through sexual contact between the two brothers, but does note that the brothers routinely shared a bed during the period when seroconversion might have occurred (Brownstein). Transmission through the sharing of injecting equipment or sexual contact is more plausible than through the sharing of a razor.

See also Medical and dental procedures and injuries for discussion of further rare routes of HIV transmission.