HIV is a relatively fragile virus—it is not easy to “catch”—and it is not spread by casual contact. In order for HIV to be transmitted, three conditions must occur: (1) there must be an HIV source, (2) there must be a sufficient dose of virus, and (3) the virus must have access to the bloodstream, mucous membranes, or broken skin of another person.
HIV can be transmitted through:
In extremely rare cases, HIV can be transmitted by sharing razors or toothbrushes if infected blood from one person was deposited on the toothbrush or razor and the blood were to enter the bloodstream of another person.
In some medical settings, other fluids—such as cerebrospinal, synovial, pleural, pericardial, and amniotic fluid—may be considered infectious if the source is HIV-positive. These fluids are generally not found outside the hospital setting. Sweat, tears, saliva, urine, and feces are not capable of transmitting HIV unless visibly contaminated with blood.
HIV transmission can occur during practices such as tattooing, blood-sharing activities like “blood brother“ rituals, or any other type of ritualistic ceremonies where blood is exchanged or when unsterilized equipment contaminated with blood is shared. HIV transmission may also occur in occupational settings.
Viral load—how much HIV is present in the bloodstream—is one of the most important predictors of the infectiousness of an HIV-positive person. Studies show a clear connection between higher viral load in the blood and increased transmissibility of HIV.
Effective prevention strategies have been identified for all routes of HIV transmission—sexual, bloodborne, and mother-to-child. UNAIDS and the World Health Organization estimate that expanded access to proven prevention strategies could avert half of the 62 million new HIV infections projected to occur worldwide between 2005 and 2015. Since no single strategy provides complete protection or is right for all individuals, a combination of methods is needed to help reduce HIV transmission.
CDC and its partners are currently pursuing a High-Impact Prevention approach to reducing the continued toll of HIV. This approach seeks to use the best mix of proven, cost-effective, and scalable interventions for high-risk populations and areas of the nation. A key element of high-impact prevention is to prioritize funding for areas with the greatest burden of HIV (CDC, 2013b).
Sexual transmission is responsible for the majority of new HIV infections. Prevention efforts have focused on behavior change programs, condoms, dental dams, HIV counseling and testing, prompt diagnosis and treatment of other sexually transmitted diseases (STDs), and male medical circumcision.
Behavioral interventions can be highly effective in reducing sexual risk behaviors and associated HIV infections. Studies in high-income countries indicate that a comprehensive risk reduction program is more effective in promoting safe sexual behaviors among young people than interventions that exclusively promote abstinence.
Behavior change programs typically have one or more aims:
Condoms are proven to be effective HIV prevention technologies, and male condoms are widely accepted and easily accessible. Female condoms are far less accepted and accessible, and have remained expensive and highly underfunded (Peters et al., 2013).
Male latex or polyurethane condoms are highly effective at preventing sexual transmission of HIV. Laboratory studies have demonstrated that latex condoms provide an essentially impermeable barrier to particles the size of HIV.
To achieve maximum protection by using condoms, they must be used consistently and correctly. Inconsistent or nonuse of condoms can lead to infection. Transmission of HIV and other STIs can occur during a single sex act with an infected partner. Incorrect use diminishes the protective effect of condoms by leading to breakage, slippage, or leakage. Incorrect use commonly occurs because of a failure to use condoms throughout the entire sex act, from start of sexual contact to finish (after ejaculation). Consistent use of condoms can reduce an individual’s risk of HIV transmission by as much as 85% (CDC, 2013b).
The importance of female condoms as a prevention method has been widely recognized. Years of empirical research confirm that female condoms have good acceptability among diverse populations, high rates of efficacy, and numerous advantages for women, men, and young people. Yet, remarkably, investment in female condom procurement and programming has been negligible in comparison to other prevention approaches.
Center for Health and Gender Equality, 2011
Reddy brand female condom. Source: Madhualla at en.Wikipedia.
The female condom is a relatively new product and has not been widely available. This is changing rapidly following the publication of design specifications by the World Health Organization in 2012. Female condoms have a number of essential features that are not found in male condoms:
Women around the world helped us design the Woman’s Condom. Photo: PATH/Glenn Austin. Used with permission.
In 2009 the U.S. Food and Drug Administration (FDA) approved the Female Condom 2 (FC2), a low-cost female condom. The FC2 is made of polyurethane fitted with larger and smaller rings at each end that help keep it inside the vagina. A soft ring at the closed end of the condom covers the cervix. Because female condoms are made of polyurethane any lubricant can be used without damaging them. Laboratory studies indicate that the female condom is an effective mechanical barrier to viruses, including HIV, and to semen (CDC, 2011).
The female condom is the only female-initiated protection method that protects against HIV, sexually transmitted infections, and unwanted pregnancy at a level equivalent to a male condom. Unfortunately, full integration of the female condom has lagged far behind in HIV prevention efforts. In the United States, studies looking at interventions aimed at high-risk populations frequently omit information and counseling on the female condom, although most studies were targeted to heterosexual risk groups. Formal CDC documents on voluntary counseling and testing do not specifically refer to the female condom as integral to the counseling approach. Adoption of the female condom into routine counseling has been inconsistent and lacking energy and funding (Gollub et al., 2013).
Other female condoms include:
Dental dams are small squares of latex that were made originally for use in dental procedures. They are now commonly used as barriers when performing oral-vaginal or oral-anal sex, or to protect the mouth from vaginal fluids or menstrual blood that could transmit HIV or other STDs.
Counseling directed at a patient’s personal risk, the situations in which risk occurs, and the use of personalized goal-setting strategies are effective STI/HIV prevention tools. One such approach, known as client-centered STI/HIV prevention counseling, involves tailoring a discussion of risk reduction to the patient’s individual situation. Client-centered counseling can increase the likelihood that a patient undertakes or enhances current risk-reduction practices, especially among persons seeking STI care (CDC, 2011b).
Timely testing and diagnosis of HIV infection also promotes HIV prevention. Infected people who are aware of their HIV status often decrease behaviors that can spread HIV. People who are not aware that they are HIV-positive are 3.5 times more likely to transmit HIV than individuals who have knowledge of their HIV-positive status.
One of the key components of the CDC’s high-impact prevention program is expanded HIV testing. The Expanded Testing Initiative helps to identify those who are unaware that they are infected with HIV. Between 2007 and 2010, the program provided nearly 2.8 million HIV tests in 25 of the U.S. areas most affected by HIV, and diagnosed more than 18,000 individuals who were previously unaware that they were HIV-positive (CDC, 2013f).
Prompt diagnosis and treatment of sexually transmitted infections (STIs) plays a critical role in efforts to prevent sexual HIV transmission. STIs such as syphilis, gonorrhea, and herpes simplex virus type 2 increase the risk of HIV acquisition and transmission by 2 to 5 times. Prompt diagnosis and treatment reduces the chance of passing on a STI to sexual partners and newborns.
In the HIV prevention toolbox of behavioral, biomedical, and structural approaches, voluntary medical male circumcision is an essential tool in all high-HIV-prevalence, predominantly heterosexual epidemic settings. It provides lifelong partial protection for men against HIV infection and reduces their likelihood of genital ulcers, syphilis, and penile cancer. Observational data and ecologic studies have suggested for decades that male circumcision provides a level of protection from HIV infection for men. Three randomized controlled trials conducted in the last decade found a 57% protective effect against HIV for men who became circumcised (Hankins et al., 2011).
Male circumcision is an old and common surgical procedure. With 30% of men globally and 67% of men in sub-Saharan Africa circumcised, social and cultural factors are the main determinants of acceptability. In sub-Saharan Africa, male circumcision was found to be acceptable to men and women in non-circumcising communities if readily accessible and provided safely. Medical male circumcision is highly cost-effective, with costs to avert one HIV infection ranging from US$ 150 to US$ 900 using a 10-year time horizon, and 1 new HIV infection averted for every 5–15 procedures performed (Hankins et al., 2011).
Exposure to HIV-infected blood is the most efficient route of HIV transmission, whether through injection drug use, tainted blood, or an occupational exposure. A number of strategies have been used to reduce the transmission of HIV via blood. These include harm reduction programs for injection drug users, securing the safety of the blood supply, and strengthening infection prevention programs in healthcare settings.
Harm reduction is an approach to community health that seeks to reduce the adverse consequences of unhealthy behaviors. In the context of drug use and HIV, harm reduction attempts to reduce the risk of becoming infected with HIV or another sexually transmitted infection. A harm reduction perspective is pragmatic and should be based on the best available evidence. Reducing HIV transmission among people who continue to inject drugs may be the clearest example of reducing a serious adverse consequence of drug use without necessarily reducing the drug use itself (Des Jarlais et al., 2013).
Harm reduction for injection drug users involves a package of services, including access to clean syringes and injection equipment, substitution drug treatment therapy, counseling, HIV and other health services, and evidence-based programs to reduce demand for drugs. The first syringe exchange program was established in The Netherlands in 1984 and was quickly expanded when HIV infection was noted among persons who inject drugs. The United Kingdom soon followed and implemented a national syringe exchange program. Australia was also quick to implement national syringe exchange programs for individuals who inject drugs (Des Jarlais et al., 2013).
In the United States, there has been strong opposition to needle-exchange programs dating back to the 1980s despite extensive evidence demonstrating that harm reduction programs reduce the risk of HIV transmission without contributing to an increase in drug use. This is related to the politics of illegal drug use and the belief that providing clean syringes to injection drug users might “encourage” drug use.
Addressing this issue is of prime importance because HIV can spread rapidly among injection drug users. Conversely, large-scale implementation of HIV prevention programs, particularly needle/syringe access programs, when HIV prevalence is very low in a population of injection drug users can keep the prevalence low (under 5%) indefinitely (Des Jarlais et al., 2013).
Very large declines in HIV incidence have been observed after large-scale implementation of evidence-based prevention programs, particularly when multiple prevention programs (needle/syringe programs, substance use treatment programs, HIV testing, and antiretroviral treatment) are implemented simultaneously (Des Jarlais et al., 2013).
HIV is very diverse and new strains continue to emerge and spread rapidly worldwide. Newly developed tests for screening the blood supply for HIV must accurately detect all the existing and emerging strains of the virus in blood samples. Although testing for HIV has reduced the risk of transmitting the virus through donated blood, there are still three challenges to keeping the blood supply safe:
Screening of a country’s blood supply is critical: receiving one or more units of HIV-infected blood results in HIV infection nearly 90% of the time. In developed countries, routine screening of the blood supply, combined with efforts to reduce unnecessary transfusions and to preclude high-risk donors, has virtually eliminated the risk of HIV transmission through donated blood. In the United States, blood donations have been screened for HIV antibodies since 1985 and for the p24 antigen since 1996.
HIV transmission has become extremely rare in healthcare settings that follow Standard Precautions, which, when properly implemented, protect patients and healthcare workers from many bacterial and viral infections, including bloodborne pathogens. Standard Precautions tell us to avoid contact with:
Employers are required to have a written exposure control plan (ECP) to eliminate or minimize employee exposures to bloodborne pathogens. The plan must be updated annually to reflect technological changes that help eliminate or reduce exposure. In the plan, employers must include information about the infection control system and infection prevention techniques used in the workplace. It should contain annual documentation of consideration and implementation of appropriate, commercially available safer medical devices designed to eliminate or minimize occupational exposure. Employers must also document that they have asked for input from frontline workers in identifying, evaluating, and selecting engineering controls.
HIV transmission from mother to child during pregnancy, labor and delivery, or breastfeeding is known as perinatal transmission and is the most common route of HIV infection in children. When HIV is diagnosed before or during pregnancy, perinatal transmission can be reduced to less than 1% if appropriate medical treatment is given, the virus becomes undetectable, and breastfeeding is avoided. Since the mid-1990s, HIV testing and preventive interventions have resulted in more than a 90% decline in the number of children perinatally infected with HIV in the United States (CDC, 2014b). From 2001 to 2012, there was a 52% decline in new HIV infections among children. Expanded access to services to prevent mother-to-child transmission prevented more than 670,000 children from acquiring HIV from 2009 to 2012 (UNAIDS, 2013a).
An estimated 260,000 children became infected with HIV in 2012, with the vast majority contracting HIV during gestation or birth or as a result of breastfeeding. It is now estimated that half of all new episodes of HIV transmission to children occur during the breastfeeding period when the majority of lactating women are not receiving the prophylaxis necessary to prevent HIV transmission (UNAIDS, 2013a).
Continuing expansion of the HIV/AIDS pandemic among women has been recognized as an exceptional challenge to global maternal health. Each year, about 1.5 million women living with HIV become pregnant and deliver. About 90% of these women live in sub-Saharan Africa, where comprehensive health services and HIV medication regimens are limited (Ngemu et al., 2014).
In the absence of interventions, the HIV-infected mother has a 15% to 45% chance of transmitting the virus to her newborn during her pregnancy or birth, or via breast milk. A worrying trend indicates that 90% of new infections in children are due to mother-to-child transmission. In 2011 around 330,000 children under the age of 15 living in sub-Saharan Africa became infected with HIV via the mother-to-child transmission pathway. Thus prevention of mother-to-child transmission is critical in curbing the spread of new HIV infections (Ngemu et al., 2014).
In prevention of mother-to-child transmission, antiretroviral drugs (known as highly active antiretroviral therapy, or HAART) that decouple links between childbirth and HIV transmission are adopted. The use of multiple drugs, often referred to as a “cocktail,” serve as powerful defenses against the ways in which the HIV virus attacks the human body. Although these drugs are not able to rid the body of HIV, they can significantly delay the onset of AIDS and potentially slow down the replication of HIV, lowering the viral load in the mother’s body and hence reducing the chances of HIV transmission (Ngemu et al., 2014).
The current World Health Organization (WHO) recommended regimen is as follows:
Complementary measures that may also be used include cesarean section and formula feeding; in some settings, the combination of all these measures has been used with variable success. However, HAART is still often described as having miraculous effects. Not surprisingly, proponents of these drugs are less anxious to discuss the times when the drugs simply do not seem to do what they are supposed to in terms of effectiveness (Ngemu et al., 2014).
The transmission of HIV through breastfeeding was first identified in 1985 and since then the issue of breastfeeding within the context of HIV and prevention of mother-to-child transmission has continued to be at the center of much debate and policy. The World Health Organization (WHO) recommends that all mothers, regardless of their HIV status, practice exclusive breastfeeding for the first 6 months of an infant’s life (Vallely et al., 2013).
In the absence antiretroviral therapy the risk of mother-to-child transmission of HIV through breastfeeding is between 20% and 45%. However, with the use of antiretroviral therapy by the mother this risk can be reduced to less than 5%, even among infants who are breastfed, because antiretroviral therapy reduces the HIV viral load in the mother’s milk.
While breastfeeding is associated with risk of transmission of HIV, exclusive breastfeeding for the first 6 months is associated with a lower risk of HIV transmission when compared to mixed feeding, even without antiretroviral therapy. The risk of infants acquiring HIV through breastfeeding, therefore, needs to be weighed against the increased risk of death from causes other than HIV, in particular malnutrition and serious illnesses such as diarrhea, among non-breastfed infants (Vallely et al., 2013).
A scheduled cesarean delivery at 38 weeks to prevent mother-to-child transmission of HIV is recommended in the following situations:
In these situations, a woman with HIV should have a scheduled cesarean delivery even if she took HIV medication during pregnancy. The cesarean delivery should be performed before a woman goes into labor and before her water breaks. Once a woman goes into labor or her water breaks, a cesarean delivery may no longer prevent mother-to-child transmission of HIV. In this situation, the decision whether to deliver the baby by cesarean section is based on medical reasons and not to prevent mother-to-child transmission of HIV (CDC, 2013d).
The risk of mother-to-child transmission of HIV is low for women who take HIV medications during pregnancy and have a viral load less than 1,000 copies/mL near the time of delivery. In this situation, a woman with HIV should have a vaginal delivery unless there are other medical reasons for a cesarean delivery (CDC, 2013d).