Substance abuse is quite common among people infected with the human immunodeficiency virus, better known as HIV. In many cases, cocaine is the preferred substance of abuse for HIV-positive people. Current evidence indicates that use of cocaine can harm the health of HIV-positive individuals in a variety of ways, including increasing the amount of the virus contained inside the body, reducing the immune system\u2019s ability to combat the virus, and contributing to patterns of behavior that worsen HIV\u2019s effects and\/or increase the likelihood of transmitting the virus to other people. Increasing HIV Viral Load Doctors refer to the amount of a virus circulating in the human bloodstream as the body\u2019s viral load. In the case of HIV, a high viral load is associated with a relatively rapid progression toward acquired immune deficiency syndrome (better known as AIDS), an immune system collapse that makes the body vulnerable to a wide range of normally harmless infectious microorganisms. On the other hand, a low viral load is associated with a slower progression toward AIDS, as well as a reduced rate of HIV-related health complications and a longer lifespan. According to the results of a study published in 2009 by the University of California, Los Angeles AIDS Institute, the presence of cocaine in the bloodstream can increase an HIV-positive individual\u2019s viral load as much as 200 times. This dramatic increase in HIV levels can occur when regular cocaine use continues for as little as two weeks. In addition to boosting the overall amount of HIV in circulation, the presence of cocaine roughly doubles the number of healthy cells in the body infected with the virus. Reduced Immune System Function HIV achieves much of its damaging effect on human health through its ability to attack, invade, and kill immune system cells called CD4 T-cells, or helper T-cells. In a functional immune system, these cells play diverse roles that include supporting the growth process of certain other immune cells and activating \u201ckiller\u201d immune cells that seek out and destroy foreign microorganisms. Without the proper amount of CD4 T-cell activity, the body\u2019s immune function will decline; in turn, a decline in immune function leaves the body increasingly susceptible to invading microorganisms that would normally not pose much of a threat. Regular use of cocaine decreases the amount of functional CD4 T-cells in HIV-infected individuals by as much as nine times, the authors of the 2009 study from the UCLA AIDS Institute report. In most cases, this degree of decline is sufficient to wipe out the vast majority of these cells. Damaging Patterns of Behavior In 2011, a group of researchers from Duke University published the results of a study that examined the effects of a wide variety of abused substances on the mental function of people infected with HIV. Specific functions assessed during the study include working memory, the ability to control impulsive behaviors, and the ability to think creatively in unusual or stressful circumstances; apart from any additional influences, HIV is known for its ability to damage each of these abilities as it progresses over time. The authors of the study concluded that the presence of cocaine inside the brain further damages the aspects of mental function already damaged by advancing HIV. Although no one can say for sure what role cocaine use plays in any given case, the combined effects of HIV and cocaine can potentially degrade an affected individual\u2019s decision-making process to the point where he or she is substantially more likely to participate in risky behaviors that make it easier for HIV to progress even further inside the body. For example, an HIV-positive cocaine user may have a decreased ability or willingness to comply with a medication routine that can keep the advance of the virus in check. An HIV-positive cocaine user may also have an increased level of involvement in sexual behaviors that inadvertently transmit the virus to currently uninfected individuals. Additional Potential Effects Cocaine is known for its ability to overstimulate the sympathetic nervous system, and thereby contribute to damaging changes in normal cardiovascular (heart and blood vessel) health. Similarly, certain medications used to slow the advance of HIV in infected individuals can also potentially damage the cardiovascular system. According to a statement released in 2011 by researchers from Emory University and Georgia State University, HIV-positive people who use cocaine can sometimes unintentionally magnify the cardiovascular damage caused by their HIV-fighting treatment regimes. When this happens, affected individuals will develop more heart- and blood vessel-related problems than either cocaine use or medication side effects would produce in isolation.