There is much we know and much we don’t know about how and why the HIV virus spreads. Yet information on the exact modes of transmission and how to combat them is critical to containing the AIDS epidemic
The Human Immunodeficiency Virus (HIV) is a virus that, once it enters the human body, weakens the immune system. The virus gradually multiplies inside the body and eventually destroys the body's ability to fight off illnesses.
This process takes a long time, and for several years after the virus enters the body, the person remains asymptomatic, that is, he or she does not suffer from any illnesses as a result of lower immunity.
This virus is passed from one person to another through blood-to-blood and sexual contact. In addition, an infected pregnant woman can pass HIV to her baby during pregnancy or delivery, as well as through breast-feeding.
This is because HIV can be transmitted through the following body fluids: blood (and any body fluid containing blood), semen, vaginal fluid, breast milk, cerebrospinal fluid (which surrounds the brain and the spinal cord), synovial fluid (which surrounds bone joints) and amniotic fluid (which surrounds a foetus). Though HIV is also present in other body fluids such as saliva and sweat, it is present in such low quantities that transmission through these routes is impossible.
HIV cannot be transmitted through casual contact between people, sharing clothes, utensils or food, or through insect bites. People with HIV may not know they are infected but can pass the virus on to others.
Risk of transmission through different routes
HIV is believed to transmit very slowly through the sexual route. Information on the risks of contracting and transmitting HIV through sexual exposures can be obtained from studies in Africa, Europe, and the US, where scientists have followed heterosexual couples in which one of the partners was infected with HIV, asked them about their sexual behaviour, and observed how many partners became infected.
These studies indicate that the estimated average risk to contract HIV through vaginal sex without a condom with an HIV-infected partner is 0.05% to 0.1% per coital act. In most such studies, less than 10% of HIV-positive men or women with HIV-negative spouses transmit HIV to their spouses in a year, even with continued unprotected sex, ie, without the use of a condom. Many general population surveys, as well as data from testing pregnant women under the programme for Prevention of Parent to Child Transmission show that between one-third and well over half of the partners of HIV-infected men or women are HIV-negative.
Receptive anal sex with an infected partner is a high-risk activity irrespective of whether the receptive partner is a man or woman. Insertive anal sex is less risky than receptive anal sex, but more risky than vaginal sex. Oral sex presents very low risk and is often seen as a safer sex option among sero-discordant couples (where one partner is HIV-positive and the other is not). The risk through unprotected oral sex, receptive or insertive, is 0.005%-0.04%.
Sexual risk is influenced by various factors. For instance, the risk of transmission is greater when the HIV-positive partner has a very new infection or is seriously ill with AIDS. This is because during these periods, semen or vaginal fluids are likely to have more viruses than at other times. Male circumcision may reduce risk to men, whereas STDs are believed to increase risk. There are also factors that are beyond our comprehension that affect sexual transmission risks, making it difficult to understand why some people get infected with HIV whereas others who seemingly have more unsafe exposures, may not.
A cubic centimetre of blood may contain as many as 100,000 to 1,000,000 or more virus particles. Many people, including health care providers, mistakenly believe that HIV dies within seconds or minutes outside the body. The fact is that outside the body, at room temperature, HIV in blood or plasma remains viable for weeks in a damp environment (eg, in a used syringe or multidose vial), and for hours if dry.
The risk that someone will become infected with HIV after a transfusion of contaminated blood is close to 100%. The risk is lower for exposures to smaller amounts of blood through scratches, jabs, cuts, or other skin-piercing events. For example, only 3 in 1,000 (0.3%) health care workers became infected with HIV after a needle-stick accident with equipment just used on an HIV-infected patient. However, most such accidents involve shallow scratches with little risk. Only about 7% of needle-stick accidents are deep enough for the hole of the needle to be within the skin (as in an injection). Therefore, the calculated average risk to seroconvert after a deep needle-stick accident is as high as 2.3%, which is significantly higher than the risk through vaginal sex, estimated at 0.05% to 0.1%.
Intravenous procedures such as an injection into a vein, or taking blood from a vein, carry higher risks if equipment is not cleaned properly between use on different patients. This is one of the reasons that injecting drug users face high risks when sharing syringes, needles or injecting equipment. Various blood exposures that carry risks of HIV transmission include injections (intramuscular, subcutaneous, intravenous), blood tests, infusions, dental care, surgery, other medical procedures, tattooing, piercing, shaving, manicures, and pedicures (when cuts occur), and needle-stick accidents.
If no care is taken to prevent mother-to-child HIV transmission, about one- third of children born to HIV-infected women will be infected, including 20% infected before or during delivery, and the remainder infected from breastfeeding.
A USAID paper estimates that breastfeeding with an HIV-infected mother transmits HIV to about 15% of HIV-negative children in two years, but other estimates are both higher and lower.
The risk through breastfeeding is cumulative; the longer the HIV-positive mother breastfeeds, the greater the additional risk of HIV transmission through breast-milk. However, if safe and adequate alternatives to breastfeeding are unaffordable or inaccessible, exclusive breastfeeding is the next best option to no breastfeeding at all. Mixed feeds, ie, combining breastfeeding with replacement feeds carries a greater risk of HIV transmission than exclusive breastfeeding.
Preventing HIV spread
To avoid getting HIV infection from sex workers and other non-regular partners one can follow the ABC approach - Abstain or Be faithful to one partner; if not, use a Condom. Further, treating any sexually transmitted diseases (STDs) that you have reduces your risk to contract HIV through unprotected sex.
To reduce the risk of HIV transmission through heterosexual sex, it is best to avoid penetrative sex with people known to be HIV-positive or who have a high risk of being HIV-positive. If this is not possible, use condoms when having penetrative sex with partners of unknown HIV status, particularly in casual relationships.
Negotiating for safe sex is an important way to protect yourself from HIV. While there is a lot of emphasis on training sex workers to negotiate for safe sex with their clients, negotiating within marriage or in short or long term relationships is often difficult. In cases where it may be difficult to negotiate for safe sex and you have doubts about your partner’s HIV status, you could seek help from a counsellor, or you may need to reconsider continuing the relationship.
In India and in other countries, there are many accounts of couples with one HIV-infected partner who have lived for years without HIV passing to the other partner. Many such couples have fathered and birthed HIV-negative children. Sero-discordant couples can have unprotected sex only when they plan to conceive, thus reducing the risk of transmission through sex, and/or take ARV treatment at the time of conception. In the future, other options may be available to prevent HIV transmission between long-term partners, such as microbicides, antiretroviral treatment to lower viral load, and prophylactic antiretroviral treatment in the HIV-negative partner. It is very probable that some options will improve with time, enabling sero-discordant couples to live with HIV as a chronic manageable disease but no longer a threat for transmission to spouses or children.
Strategies to prevent HIV acquisition for men having sex with other men (MSM) include knowing a partner’s HIV status (so that one can decide what precautions to take); being mutually faithful; using a condom, especially for anal sex; and avoiding penetrative sex. Receptive anal intercourse is by far the most efficient sexual act for acquiring HIV, but significant risk also exists with insertive anal sex.
Mother-to-child HIV transmission
Most mother-to-child HIV transmission can be prevented. In 2001, the National Aids Control Organisation (NACO) and government health departments began testing pregnant women and offering medical interventions to protect children from HIV infection.
The government’s programme for the Prevention of Parent To Child Transmission (PPTCT), which is available in many public hospitals, tests pregnant women to find those who are HIV-positive, counsels them, and provides antiretroviral drugs for HIV-positive mothers and infants to prevent HIV transmission. These drugs reduce HIV transmission to 10%. This rate can be further lowered to less than 2% with better combinations of antiretroviral drugs, which are available through the private sector, along with caesarean delivery and avoiding breastfeeding.
Those who do not have access to clean water, or who are unable to ensure sterility of the bottles, spoons, cups etc that are used to feed babies, may need to weigh the relative risks to their child’s health from unclean water and/or inadequate feeds, and breastfeeding. Other infant feeding options that may be available to babies of HIV-positive mothers include wet-nursing by known HIV-negative mothers, expressing and heat-treating breast milk, and breast-milk banks.
Technology and public programmes to prevent mother-to-child transmission have been changing rapidly. The best and latest advice to prevent mother-to-child transmission would be available from public hospitals, and State AIDS Control Societies (SACS). Services to prevent mother-to-child transmission is also available at some private health facilities, but care should be taken when accessing the private sector as there are many private doctors who give mixed messages and irrational treatment.
Injecting drug use
For those who cannot or will not stop injecting drugs, there are various ways to prevent infection with HIV and other blood borne viruses. You could avoid sharing needles, syringes, water or drug preparation equipment, and use syringes obtained from a reliable source. If new, sterile syringes and other drug preparation and injection equipment is not available, then previously used equipment should be boiled in water or disinfected with bleach before re-use.
Injection drug users and their sex partners should take precautions such as using condoms consistently and correctly, to reduce risks of sexual transmission of HIV.
Other harm reduction methods are to switch to oral substitutes. Buprenorphine and methadone are commonly used opioid substitutes given under medical supervision to injecting drug users. The former is being increasingly used among NGOs working with IDU in different parts of the country. Opioid substitution therapy is also a part of the next phase of the National AIDS Control Programme (NACP III). For those who can and are willing to give up drugs altogether, detoxification, rehabilitation and other therapies are available in many parts of the country.
Other blood exposures
Unsterile practices are common in India, exposure to which could result in HIV infection. Blood for transfusions should be taken only from registered blood banks as these are now all tested to ensure that they are free from HIV.
Ideally, avoid skin piercing procedures like tattooing, piercing, and unnecessary injections and infusions. When you have to be exposed to skin piercing exposures, use new disposable instruments. For instruments that have to be reused, like dental equipment, be sure they have been sterilised. Express your concerns to your health care providers and ask them to change their practices where necessary. If you are not sure about the sterility of equipment and cannot negotiate for safe care, change your provider.
Providers often excuse themselves from treating people living with HIV on the grounds that they do not have adequate facilities to protect themselves. However, the only way that health care providers can protect themselves is to assume that all patients are potentially infectious and protect themselves in the same way that they would when treating a person known to be infected with the virus. The fact that HIV survives for a long time outside the human body, is a risk faced by both health care workers and patients. In fact, acknowledging the risks that health care providers face in administering care, the government has a programme where health providers are given medication after a possible risky exposure to HIV (post-exposure prophylaxis) to prevent them from getting infected.
- Varghese B, Maher J E, Peterman T A, Mranson B M, Steketee R W: ‘Reducing the risk of sexual HIV transmission: quantifying the per-act risk for HIV on the basis of choice of partner, sex act, and condom use’, Sexually Transmitted Diseases, 2002; 29: 38-43
- Vittinghoff E, Douglas J, Judson F, McKirnan D, MacQueen K, Buchbinder S P: ‘Per-contact risk of human immunodeficiency virus transmission between male sexual partners’, American Journal of Epidemiology, 1999; 150: 306-311.
- Abdala N, Stephens P C, Griffith B P, Heimer R: ‘Survival of HIV-1 in syringes’, Journal of Acquired Immunodeficieny Syndrome, 1999; 20: 73-80.
- Resnick L, Veren K, Salahuddin S Z, Tondreau S, Markham PD: ‘Stability and inactivation of HTLV-III/LAV under clinical and laboratory conditions’, JAMA 1986; 255: 1887-1891.
- Gisselquist D: ‘Estimating HIV transmission efficiency through unsafe medical injections’, International Journal of STD, 2002; 13: 152-159
- Gisselquist and Correa: ‘How much does heterosexual commercial sex contribute to India’s HIV epidemic?’, International Journal of STD & AIDS, 2006; 17: 736–742
- NACO Facts and figures: HIV estimates – 2003. Available at: www.nacoonline.org/
- Piwocs EG: HIV/AIDS and infant feeding: risks and realities in Africa. Washington DC: USAID, 2000.
- NACO Monthly updates on AIDS (31st July, 2005). Available at: http://www.nacoonline.org/
- India-Canada Collaborative HIV/AIDS Project (ICHAP): ‘Community-based HIV prevalence study in ICHAP demonstration project area, key findings’, Bangalore: ICHAP, 2004.
- Tamil Nadu State AIDS Control Society: Activities of TANSACS. Chennai: TANSACS, 2005.
- Mehendale S M, Rodrigues J J, Brookmeyer R S, et al: ‘Incidence and predictors of human immunodeficiency virus type 1 seroconversion in patients attending sexually transmitted disease clinics in India’, Journal of Infectious Diseases, 1995; 172: 1486-1491.
- Arora N K, Mathew T, Devi SR, et al: ‘Assessment of Injection Practices in India (2002-03)’: An InCLEN Program Evaluation Network Study, New Delhi, All India Institute of Medical Sciences, 2006. Available at: http://www.ipen.org.in/index.php?option=content&task=
- Hauri A J, Armstrong G L, Hutin YJF: ‘The global burden of disease attributable to contaminated injections given in health care settings’, International Journal of STD AIDS, 2004; 15: 7-16.
- Singhal T: ‘Burden of HIV in India due to unsafe injections and blood transfusions’, MSc thesis submitted to University of London, 2002.
- Banerjee K, Rodriques J, Israel Z, Kulkarni S, Thakar M: ‘Outbreak of HIV seropositivity among commercial plasma donors in Pune, India’, The Lancet, 1989; ii: 166.
- Christiansen C B, Nielsen C, Machucca R: ‘Cluster of HIV-1 infection among children in Indian Hospital in Bombay’, Informal report to WHO, September 1998. Department of Virology, Statens Serum Institut, Copenhagen, Denmark.
InfoChange News & Features, March 2008