Disease burden

Throughout the world, HIV is one of the leading causes of death and results in more deaths than any other disease caused by infection. As of 2007, approximately 33.2 million people were infected with HIV. Approximately 2.5 million living with this infection were children, and 2.5 million new diagnoses were made that year—7400 new cases each day. More than 2 million people die every year due to AIDS. Almost all of those people living with HIV reside in countries with low or middle incomes.

Sub-Saharan Africa has been hit especially hard (WHO, 2008). This region contains more than 65% of the world’s HIV population and accounts for 76% of the total mortality rate attributed to AIDS (Henry J. Kaiser Family Foundation, 2007). It is estimated that by the year 2010, 18 million children in that region will lose both of their parents to AIDS. Death related to AIDS is largely associated with poor health care access for prevention and treatment services (Henry J. Kaiser Family Foundation, 2007). During the past 2 years the number of people infected with HIV has declined. This decreasing infection rate is thought to be related to increased access to antiretroviral treatments. Managing and treating this disease will remain a challenge for years to come, especially in the sub-Saharan region of Africa.

In the United States approximately 56,000 new cases of HIV are diagnosed each year (Hall et al., 2008). More than 1 million people in the United States are currently living with HIV/AIDS (Henry J. Kaiser Family Foundation, 2007). Between 2003 and 2006, the number of new HIV/AIDS cases in the United States stabilized, while the number of people who were living with the disease increased. At the end of 2006, almost 500,000 people were infected and living with HIV/AIDS (CDC, 2008). California, Florida, and New York accounted for most of the patients with AIDS diagnoses (CDC, 2008).

Injecting drug use

HIV may be transmitted by exposure to contaminated blood through the accidental or intentional sharing of injecting equipment and paraphernalia. Such equipment includes syringes, needles, cookers (spoons or bottle caps used for mixing the drug), and filtering devices (such as cotton balls). Injecting drug users represent the second highest exposure category, following the MSM category (CDC, 2006). Although typically seen in large metropolitan areas, injecting drug use occurs in smaller cities and rural areas as well. Injection is not limited to illicit drugs; HIV can be transmitted via contaminated “works” used to inject steroids, vitamins, and insulin.

Injecting drug users confirm needle placement in a vein by drawing back blood into the syringe; the substance is then injected into the vein. They may also draw blood back into the syringe and inject numerous times, a procedure called “booting.” This ensures that no substance remains in the syringe. Other factors that put injecting drug users at risk for HIV include poor nutritional status, poor hygiene, and impaired judgment due to mood-altering substances. The long-term effects of injecting drug use put individuals at increased risk for other diseases, such as hepatitis B, hepatitis C, and other bloodborne illnesses.

Blood and blood products

Since 1985, blood banks in the United States have screened all donated blood for HIV-1 antibodies, and since 1992 they have also screened for HIV-2. Blood banks have also implemented procedures to find blood donors who might be at high risk for being infected with HIV. Blood from donors who are deemed high risk or that tests positive for HIV is discarded. In addition to HIV, blood is currently screened for HTLV-1, HTLV-2, hepatitis B virus, syphilis, and hepatitis C virus.

Every year, a small number of blood donations come from donors who are infected with HIV but in whom the HIV antibody was undetected. When a blood donor has not yet undergone seroconversion (a change in serologic test results from negative to positive as antibodies develop in reaction to an infection), the current HIV antibody test is unable to detect the infection. In the past there was a 22-day window where the donor could donate HIV-infected blood that would not be detected by the HIV-1 and HIV-2 antibody test. Since 1995, however, blood has also been screened for HIV-1 p24 antigen. With this addition, this window has been reduced to 16 days. In 1999, another test called the nucleic acid amplification test was introduced. This test detects HIV-1 ribonucleic acid (RNA) and has reduced the window again to only 11 days. By 2003, after 25 million donations, only three people were infected with HIV after receiving a blood product transfusion. The blood came from two separate donors, and the blood tested negative for HIV with all currently available HIV tests (Donnegan, 2003).

Before 1985, people who received replacement clotting factors for blood coagulation difficulties had an increased risk of contracting HIV. Since 1985, a recombinant technique is used to manufacture the clotting factors or the clotting factors are treated with chemicals or heated to kill the HIV.

Occupational exposure

Almost 25,000 adults who developed AIDS before 2003 were health care workers. This represents 5% of all AIDS cases among adults who had a known occupation.

According to the CDC, there is a distinction between a “documented” and a “possible” HIV seroconversion. When the infection is documented, it means that the individual had a documented exposure related to the occupation and developed HIV. A possible infection indicates that the individual worked in a high-risk setting with exposure to blood or other body fluids related to his or her occupation. However, there was no documented exposure event.

In the United States at the time this was written, 46% (26) of the 57 health care workers who were infected with HIV as a result of a documented occupational exposure had developed AIDS. Of those health care workers with possible exposures, 121 of 138 developed AIDS (Sepkowitz & Eisenberg, 2005). Of all health care workers with HIV, most did not have a documented exposure, and the source of their infection is thought to be from high-risk sexual behavior.

Most of the health care workers who have been infected with HIV are nurses. The second largest group is laboratory clinicians, and the third largest group is physicians (nonsurgical). Other health care workers with possible exposures included emergency medical technicians, health care aides, housekeepers, and maintenance workers. Most of the infections occurred after a needlestick injury with resulting puncture wound. There is thought to be some underreporting of exposures because it is voluntary. If a health care worker does have a needlestick resulting in exposure to a known HIV-infected person, the risk for contracting HIV is low, at just about 0.3%.

As of this writing, the last new HIV case involving a possible exposure to an HIV/AIDS patient was in 2000 (CDC, 2007f). Some cases are still being investigated.

Needlesticks that occur when a health care worker is exposed to known HIV-infected persons are known as percutaneous exposure. If the exposure involves a hollow-bore needle filled with blood that is placed in the patient’s vein or artery, then the transmission risk of HIV is increased. Also, the transmission risk is increased if the health care worker suffers a deep injury at the time of the exposure. Scalpels, suture needles, and smaller gauge injection needles also pose a risk for transmission, but it is much smaller. If only the mucous membranes are exposed during the incident, then the risk for seroconversion is only 0.09%. There is a small risk for seroconverting if the health care worker’s skin is not intact and is exposed to blood or body fluids.

Unfortunately, postexposure antiviral therapy given to health care workers after a documented exposure may result in severe hepatitis that may require a liver transplant. Some health care workers have died after documented or possible exposure to HIV, but that number has not been reported at this time.

Perinatal (vertical) transmission

HIV infection can be transmitted from a mother to her infant during pregnancy, at the time of delivery, or after birth through breastfeeding. In the United States, it is estimated that approximately 30% of infected mothers will transmit HIV to their infants, with approximately 50% to 70% of the transmissions occurring late in utero or intrapartum. For unknown reasons, the rate of vertical transmission varies around the world; the rate in France is around 11%, but it is nearly 50% in parts of Africa. Factors such as the stage of maternal HIV disease (it is more likely to be transmitted during the initial and later stages of infection, when more of the virus is circulating in the mother’s blood and body fluids), a decreased CD₄⁺ count or high viral load, the presence or absence of STIs, and the mother’s nutritional status all play a role in vertical transmission. Factors that increase the risk of transmission during delivery include extreme prematurity; complicated pregnancies leading to extended labor; the mixing of maternal and fetal blood; newborn ingestion of maternal blood, amniotic fluid, or vaginal secretions; skin excoriation in the newborn; and being the first child born in a multiple gestation.

In 1994 the AIDS Clinical Trials Group (ACTG) 076 study demonstrated that a plan of zidovudine therapy started after the 14th week of gestation, given intravenously to the mother during delivery and including zidovudine syrup given to the infant after birth, reduces the risk of HIV transmission by 67% (Perinatal HIV Guidelines Working Group, 2001). The long-term effects of zidovudine or combination therapy are not known, but anecdotal evidence suggests that polydactyly (the congenital presence of more than the normal number of fingers and toes) and ventricular septal defect may be caused by zidovudine. It is difficult to determine whether these defects are caused by in utero exposure to the drug or whether the incidence is the same as in the general population. Children who received zidovudine in the womb and for the first 6 weeks of life are closely monitored by authorities to document any long-term side effects.

In addition to drug therapy, substantial advances have been made in understanding the pathophysiology, treatment, and monitoring of HIV infection. These advances have resulted in changes in the standard of care for individuals, including pregnant women, with HIV infection. More aggressive combination drug regimens that provide maximal viral suppression are now recommended. Although pregnancy alone is not a reason to defer treatment, the use of anti-HIV drugs during pregnancy requires special consideration. Unfortunately, no long-term data regarding the long-term effects on the fetus exist. Because of this, offering antiretroviral therapy (ART) to HIV-infected women—whether to primarily treat HIV infection or to reduce the likelihood of perinatal transmission—should be accompanied by a discussion of the known and unknown short- and long-term benefits and potential risks. Because of the findings of ACTG 076, zidovudine should be a part of this treatment regimen.

An HIV-positive pregnant woman should be given this information to make an informed decision about treatment options. Current recommendations call for routine HIV counseling and voluntary HIV testing of pregnant women and those women considering pregnancy. However, there are no legal requirements that a woman take zidovudine during pregnancy or that she be tested for HIV antibodies.

The HIV transmission rates from mother to child have been reduced due to several recommended interventions. This includes ART, formula feeding, and cesarean section. In developed countries, this number has decreased from 25% (without interventions) to less than 2%. In countries where ART is not available and mothers continue to breastfeed, by age 2 the infection rate for babies born to HIV-infected mothers can be as high as 25%. Infants born to HIV-infected mothers have positive HIV antibody results as long as 15 to 18 months after birth. This is caused by maternal antibodies that cross the placenta during gestation and remain in the infant’s circulatory system. An earlier diagnosis of HIV infection can be made by doing an HIV viral culture or by measuring the amount of HIV RNA or viral load through a technique called polymerase chain reaction (PCR) or branched chain DNA testing (bDNA).