Not likely, say doctors, as there are very low levels of the virus in one’s saliva. JOAN CHEW looks at the common misconceptions about HIV and how the virus is transmitted
There are many misconceptions about HIV and one is that the virus can be passed through saliva, sweat, tears and urine. The truth is that while the virus has been found in these body fluids of some HIV-positive people, they are in such low quantities that nobody has ever been infected through them, said Dr Asok Kurup, a infectious diseases specialist in private practice.
HIV is passed most readily through blood, semen, vaginal secretions and breast milk. Of the 463 cases last year, 449 – or more than 95 per cent – were infected through sexual contact. The same was observed for the 169 Singaporeans detected to be HIV-positive in the first six months of this year, according to figures released by the Ministry of Health (MOH) last Sunday.
The total number of HIV infected Singaporeans stands at 4,573 currently, with 1,356 of them dead. So kissing, hugging, shaking hands and sharing meals and toilet seats with a HIV-positive person carries no risk of HIV transmission. In fact, saliva is a good agent for destroying the virus.
Misconceptions about HIV have led to unfounded fears and stigma against people living with the virus. It is probably ignorance – and the stigma attached to the virus – that has contributed to the low rate of HIV testing here. The MOH reported a 7 per cent drop in the number who seek anonymous testing from January to October this year, compared to the same period last year.
How the virus is transmitted
Dr Kurup, also a visiting consultant at the department of infectious diseases at Singapore General Hospital, said that for infection to occur, a person must be exposed to pre-ejaculate fluid, semen, vaginal secretions, blood or breast milk. These body fluids contain high concentrations of HIV, with the highest being in blood, then semen, vaginal secretions and breast milk, he said.
People are infected through unprotected vaginal, anal and oral sex, intravenous drug use, blood transfusions or from mother to baby before, during and after delivery through breastfeeding. The virus must get into a person’s bloodstream and spread to other organs for infection to occur, added Professor Roy Chan, president of AFA and director of the National Skin Centre.
During sexual intercourse, HIV passes through the mucous membranes in the genitals or the rectum. But an infected partner is unlikely to pass on the virus through the saliva because of the unique environment in one’s mouth. “In the oral cavity, there is a thick topmost layer of skin, a low number of specific cells which HIV targets and the presence of antiviral antibodies,” said Dr Kurup. “HIV thus exists in impossibly low levels in the mouth such that it becomes non-infectious.” Prof Chan said the presence of certain types of proteins, antibodies and other substances in saliva inactivates the virus. However, the risk of transmission still exists if an infected person has blood in his or her mouth.
Oral sex is risky
Prof Chan said that though the risk of contracting HIV through oral sex is extremely low, it is not zero. He said: “If a HIV-infected person has blood in his or her mouth during oral sex, HIV can enter the partner through the lining of the urethra, vagina or anus.” On the other hand, a HIV-free partner who has mouth ulcers, lesions or gingivitis (inflammation of the gums) could become infected through contact with the semen or vaginal fluid of a person who is HIV-positive.
In such a situation, the antiviral mechanisms in the mouth would not be sufficient to prevent HIV transmission. However, healthy, intact skin is an effective barrier against the virus. An infection-free person who is in contact with only his HIV-positive partner’s saliva runs a lower risk of infection than another person who is in contact with his partner’s body fluids like semen, said Dr Kurup.