Human immune deficiency virus (HIV) causes the disease Acquired Immunodeficiency syndrome popularly known as AIDS (abbreviated form). HIV causes destruction of the immune system and invites life threatening infections like tuberculsosis (TB), cytomegalo virus (CMV), systemic fungal infections and many other opportunistic entities which kill the patient early. HIV infection evolves through several stages after transmission from a HIV positive person to a negative one. AIDS is the end stage of HIV infection which is potentially lethal if not controlled with antiretroviral therapy (ART). No curative treatment is available for this virus till date.

However, with the advent of ART the patients have got increased life expectancy and fewer incidences of opportunistic infections. HIV/AIDS comes with many social stigmata and has its own myths and controversies regarding its transmission. There are various beliefs and interpretations among people all over the world regarding the nature and modes of HIV transmission. It has extremes of variations. The well known and study proven modes of transmissions are blood bourn (due to blood transfusion, intravenous drug users sharing needles, heterosexual or homosexual intercourse, HIV infected mother to foetus or breastfed infants of an HIV infected mother.

Recently, HIV was proven to get transmitted through contact with eye secretion or tears and to some extent through saliva. Kissing is not known to be a conventional mode of HIV transmission because of very low or infinitesimally low concentration of virus in saliva (thanks to the salivary lysozyme). However, few case reports from all over the world have postulated saliva as a possible mode of transmission. It is till date a controversial topic which has no research based evidence. Few studies from different geographical locations which tested the belief of people regarding the transmission of HIV through saliva found that it is strongly believed by most of the people (>50%) that deep kissing leads to HIV transmission.

Since, many people who contract the disease hide their HIV positive status due to social stigma are potential source of HIV infection and can transmit the disease silently through many ways as depicted above. The risk of having opportunistic infections like oral or esophageal candidiasis, herpes labialis, angular stomatitis, chilitis are very high among immunocompromised hosts and these infection per se can breach the oral protective mucosal layer to cause potential transmission through contact of the other non infected person’s mucosal surface of oral cavity. But there is a very negligible chance. This is because HIV gains entry through a breached or ruptured skin or mucus membrane.

 This is why a woman has a much higher chance of transmission through infected seminal deposits in vagina due to tinny micro abrasions during intercourse and a much greater surface of vagina compared to that of glans penis. Therefore, men have lesser chance compared to women in case of one to one transmission of HIV. The chance of transmission in anal sex is much higher because the anal mucosa has thin layer and prone to breach by anal intercourse. However, oral cavity is protected by a salivary enzyme called lysozyme which has microbial killing property. Due to the low concentration of HIV in saliva of the infected person the probability of acquiring the disease is very less.

The same is not true when the peri-oral skin, lips and lining of the oral cavity is breached due to some ulcer, cut or dental infections. The Centre for Disease Control (USA) has specified modes of transmitted of HIV which does not include social or closed kissing. There is relative risk of HIV transmission if an HIV infected person with oral lesions (sore which is oozing and/or bleeding gums) performs a deep, open-mouth, prolonged kissing on a negative partner who is having similar oral hygiene. In this case it is important to know that here blood to blood contact inside the oral cavity is necessary. HIV is not known to spread through saliva.

However, few case reports have depicted transmission of HIV in children through pre-chewed food. The three forms of oral sex viz. fellatio where mouth is put on penis or cunnilingus (vagina) and rimming (anus) have very little chance of HIV transmission. However, it is theoretically possible to acquire HIV infection through swallowing semen of an infected person.

The risk of HIV transmission from different modes or routes are depicted below Activity Risk-per-exposure a) Mother-to-child Mother takes at least two weeks ART Mother takes combination therapy, viral load below 50 0.8% 0.1% b) Injecting drug use Estimates range from 0.63% to 2.4% c) Needlestick injury, no other risk factors 0.13% d) Blood transfusion with contaminated blood 92.5% e) Sexual Intercourse Risk-per-exposure f) Vaginal sex High-income countries Low-income countries Female-to-male 0.04% 0.38% Male-to-female 0.08% 0.30% source partner asymptomatic late-stage disease 0.07% 0.55% g) Receptive anal sex Gay men, partner unknown status Gay men, partner HIV positive With condom, gay men, partner unknown status 0.27% 0.82% 0.18% h) Insertive anal sex, gay men, partner unknown status Without condom With condom 0.06% 0.04% i) Receptive fellatio Estimates range from 0.00% to 0.04%

It is important to know that HIV transmission depends not only on route but also on several othe factors like the clinical stage of HIV infection, CD4 cell count, viral load, virulence of the virus, host immune status like LTNP (long term non-progressor), prevalence of HIV in the community, antiretroviral therapy (ART) naïve or on ART, amount of exposing body fluid or surface area of contact and lastly the route of entry. Many people seek precise advice from a medical practitioner or a HIV care giver about chance of getting HIV/AIDS from different human behaviours or habits. It is not to be taken as a dictum that HIV transmission cannot occur through salivary route. It can interpreted that the chance of getting an infection is very less (almost equal to that with an intact skin) through kissing. One can avoid deep kissing with a known HIV positive patient. Oral hygiene is the key factor hence; need to be taken care of.

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