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Continuing Education for Health Professionals

Washington: HIV/AIDS, 7 units

Module 1

Part I: Etiology and Epidemiology of HIV/AIDS

Bulletin

In 2011 United Nations member states signed off on a set of targets and commitments aimed at reversing the spread of HIV and AIDS throughout the world. Called the Millennium Development Goals, the 193 member countries set 10 goals to be achieved by 2015. The overall purpose is to halt and begin to reverse the HIV epidemic by 2015. This commitment by member nations has had a profound effect and represents unprecedented cooperation and agreement toward the eventual elimination of HIV.

UNAIDS, 2014

The human immunodeficiency virus (HIV) has infected tens of millions of people around the globe in the past three decades, with devastating results. In its advanced stageacquired immunodeficiency syndrome (AIDS)the infected individual has no protection from diseases that may not even threaten people who have healthy immune systems. While medical treatment can delay the onset of AIDS, no cure is available.

Definition of HIV and AIDS

The human immunodeficiency virus (HIV) kills or impairs the cells of the immune system and progressively destroys the body’s ability to protect itself. Over time, a person with a deficient immune system (immunodeficiency) may become vulnerable to infections by disease-causing organisms such as bacteria or viruses. These infections can become life-threatening.

The term AIDS stands for “acquired immunodeficiency syndrome,” and it refers to the most advanced stage of HIV infection. Medical treatment can delay the onset of AIDS, but HIV infection eventually results in a syndrome (combination) of symptoms, diseases, and infections. The diagnosis of AIDS requires evidence of HIV infection and the appearance of some specific conditions or diseases. Only a licensed medical provider can make an AIDS diagnosis.

All people diagnosed with AIDS have HIV, but an individual may be infected with HIV and not yet have AIDS.

HIV-Infection in the Body

Human Lymphocyte Showing HIV Infection

image: lymphocyte showing HIV

A scanning electron micrograph showing HIV-1 virions (in green) on the surface of a human lymphocyte. HIV was identified in 1983 as the pathogen responsible for AIDS. In the infected individual, the virus causes a depletion of T-cells, which leaves these patients susceptible to opportunistic infections and to certain malignancies. Source: Public Health Image Library, image #11279, CDC, 1989.

HIV “Budding” Out of a T-cell

image: HIV budding out of a T-cell

Source: NIAID, courtesy of Dr. Tom Folks.

HIV enters the bloodstream and seeks out T-helper lymphocytes, white blood cells essential to the functioning of the immune system. One of the functions of these cells is to regulate the immune response in the event of attack from disease-causing organisms such as bacteria or viruses. When the virus infects the T-helper lymphocyte, the cell sends signals to other cells, which produce antibodies. This T-helper lymphocyte cell may also be called the T4 or the CD4 cell.

Antibodies (proteins made by the immune system in response to infection) are produced by the immune system to help get rid of specific foreign invaders that can cause disease. Producing antibodies is an essential function of our immune systems. The body makes a specific antibody for each disease. For example, if we are exposed to the measles virus, the immune system will develop antibodies specifically designed to attack that virus. Polio antibodies fight the polio virus.

When our immune system is working correctly, it protects against these foreign invaders. HIV infects and destroys the T-helper lymphocytes and damages their ability to signal for antibody production. This results in the eventual decline of the immune system.

Primary HIV Infection

Primary HIV infection (acute HIV infection) is the first stage of HIV disease. It begins with initial infection and typically lasts only a week or two. During this time the virus is establishing itself in the body but the body has not yet begun to produce antibodies. Because of this, the infection cannot be discovered by any HIV tests.

This period of acute infection is characterized by a high viral load (large numbers of the virus) and a decline in CD4 cells. Perhaps half of infected patients experience mononucleosis-like symptoms (fever, swollen glands) during primary infection, but the symptoms are not life-threatening and may be misinterpreted as a minor illness.

During primary infection, newly infected people can infect partners because they do not yet know they have HIV. The primary infection period ends when the body begins to produce HIV-specific antibodies. The number of antibodies is still insufficient to be detectable by HIV testing.

Window Period

The window period is the period of time between initial infection with HIV and when the body produces detectable antibodies, which can vary from 2 to 12 weeks. During the window period a person is infectious, with a high viral load and a negative HIV antibody test. This means the infected person might get a negative result while actually having HIV.

The point when the HIV antibody test becomes positive is called the point of seroconversion.

Asymptomatic Stage

After the acute stage of HIV infection, people infected with HIV continue to look and feel completely well for long periods, sometimes for many years. During this time, the virus is replicating and slowly destroying the immune system. This asymptomatic stage is sometimes referred to as clinical latency.

This means that, although a person looks and feels healthy, they can infect other people through unprotected anal, vaginal, or oral sex or through needle sharingespecially if they have not been tested and do not know that they are infected. The virus can also be passed from an infected woman to her baby during pregnancy, birth, or breastfeeding. Without antiretroviral therapy, it takes an average of 10 years between the time a person is infected with HIV and the onset of AIDS.

The Origin of HIV

Since HIV was discovered in 1983, researchers have worked to pinpoint the origin of the virus. In 1999 an international team of researchers reported that they discovered the origins of HIV-1, the predominant strain of HIV in the developed world. A subspecies of chimpanzees native to west equatorial Africa was identified as the original source of the virus. The researchers believe that HIV-1 was introduced into the human population when hunters became exposed to infected blood. The transmission of HIV is driven by changes in migration, housing, travel, sexual practices, drug use, war, and economics that affect both Africa and the entire world.

HIV Strains and Subtypes

HIV has divided into two primary strains: HIV-1 and HIV-2. Worldwide, the predominant virus is HIV-1, and generally when people refer to HIV without specifying the type of virus they are referring to HIV-1. The relatively uncommon HIV-2 type is concentrated in West Africa and is rarely found elsewhere.

HIV is a highly variable virus that mutates very readily. This means there are many different strains of HIV, even within the body of a single infected person. Based on genetic similarities, the numerous viral strains may be classified into types, groups, and subtypes.

Both HIV-1 and HIV-2 have several subtypes. It is virtually certain that more undiscovered subtypes are in existence now. It is also probable that more HIV subtypes will evolve in the future. As of 2001, blood testing in the United States can detect both strains and all known subtypes of HIV.

Epidemiology of HIV and AIDS

Epidemiology is “the study of how disease is distributed in populations and of the factors that influence or determine this distribution.” Epidemiologists try to discover why a disease develops in some people and not in others. AIDS was first recognized in the United States in 1981. In Washington State, the first reported case of AIDS was in 1982. Since then, the number of AIDS cases has continued to increase both in the United States and other countries. In 1983 HIV was discovered to be the cause of AIDS.

People who are infected with HIV come from all races, countries, sexual orientations, genders, and income levels. Globally, most of the people who are infected with HIV have not been tested, and are unaware that they are living with the virus. The U.S. Centers for Disease Control and Prevention (CDC) estimates that in 2012, 20% of those in the United States who had HIV were unaware that they were living with the virus. This is a decline from the 25% measured in 2003 and is a positive sign because research shows that most individuals who know they are infected with HIV will reduce behaviors that could transmit the virus (CDC, 2012; 2011).

It is important to note that the great majority of persons with HIV infection do not transmit HIV to others. The CDC estimates that in 2006 there were 5 transmissions per 100 persons living with HIV infection. This means that at least 95% of those living with HIV infection did not transmit the virus to others that year. This represents an 89% decline in the estimated rate of transmission since the peak level of new infections in the mid-1980s. It is believed that the decline is due to effective prevention efforts and the availability of improved testing and treatments for HIV (CDC, 2011).

CDC has estimated that more than 1 million (1,178,350) adults and adolescents were living with HIV infection in the United States at the end of 2008. This is an increase of approximately 7% from the previous estimate in 2006. The increase is due to a higher number of people becoming infected with HIV than the number of people who die each year with HIV or AIDS (CDC, 2012).

Despite increases in the total number of people in the U.S. living with HIV infection in recent years (due to better testing and treatment options), the annual number of new HIV infections has remained relatively stable. However, new infections continue at far too high a level, with approximately 50,000 Americans becoming infected with HIV each year. And, too many are still being diagnosed late in the course of infection, which means that opportunities for treatment and prevention are being missed (CDC, 2011).

Overall, nearly 619,400 people with an AIDS diagnosis in the United States have died from the beginning of the epidemic through 2009. From 2006 through 2008, the annual estimated rate (per 100,000) of deaths of persons with an AIDS diagnosis decreased 7%. Interpreting data regarding deaths of persons with a diagnosis of HIV or AIDS can be difficult because many factors can affect the data. (CDC, 2012; 2011).

In July 2012 UNAIDS released Together we will end AIDS, an important report that looks at current data on such markers as new infections, persons receiving treatment, deaths, and HIV among children, but also addresses scientific and social programs, economic issues, the 2011 Political Declaration on HIV and AIDS, and the need for shared responsibility worldwide in the fight against HIV and AIDS. UNAIDS estimates there were 34.2 million people in the world living with HIV or AIDS in 2011. In that year 2.5 million people worldwide were newly infected with HIVa 20% reduction since 2001, and new infections among children decreased by 24% between 2009 and 2011 (UNAIDS, 2012a, 2012b).

Young people between the ages of 15 and 24 account for 40% of new infections, a 5% decline, but in that age group, infection rates among women are twice that of men and women make up 63% of those living with infection. After decades of increasing mortality, the annual number of AIDS deaths globally finally saw a two-year decline to just over 2 million people in 2007 and in 2011 that number was about 1.7 milliona decline of 24% since the peak in 2005 (UNAIDS, 2012; 2008).

Global Prevalence of HIV, 2010

image: HIV prevalence map

Figure 2.4 from page 23 in UNAIDS Report on the global AIDS epidemic 2010.

The discovery of combination antiviral drug therapies in 1996 resulted in a dramatic decrease in the number of deaths due to AIDS among people given the drug therapies. Many people who have access to the therapies may not benefit from them, or may not be able to tolerate the side effects. The medications are expensive and require strict dosing schedules. In developing countries, many people with HIV have no access to the newer drug therapies.

HIV and AIDS Cases Are Reportable

AIDS cases have been reportable (physicians must confidentially report any cases among their patients) to the CDC since 1984, when the existence of the syndrome that follows HIV infection was clearly established. AIDS and symptomatic HIV infections have been reportable to the Washington State Department of Health (DOH) since 1984 and 1993, respectively. HIV cases became reportable to the Washington State Department of Health in fall 1999.

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