HIV (human immunodeficiency virus) is the virus that causes AIDS (acquired immunodeficiency syndrome). If untreated, HIV can progressively destroy the body's ability to fight infections and certain cancers. It can weaken the immune system by infecting lymphocytes, a type of white blood cell, that normally help the body fight infections. Specific lymphocytes known as T-helper cells or CD4 cells are major targets for HIV. The virus binds to CD4 cells, enters them, replicates inside them, and eventually kills them.
Over time and without treatment, the amount of HIV virus—the viral load—can increase while the number of CD4 cells in the blood declines. After several years without treatment, the number of CD4 cells can drop to the point that AIDS-associated conditions and symptoms begin to appear. AIDS treatments can slow and even precent the disease from progressing by reducing the amount of HIV in the body. This allows the body's CD4 cells to increase or stabilize.
The Centers for Disease Control and Prevention (CDC) estimates that about 38,000 people in the U.S were diagnosed with HIV in 2018, the year with the most current statistics. Additionally, 1.2 million people in the U.S. are living with HIV infection, and nearly 14% of those with the infection are not aware of it and can pass the virus on to others. In 2018, nearly 16,000 people diagnosed with HIV died. These deaths may be due to any cause.
Worldwide, 690,000 died of AIDS-related illnesses in 2019 and 38 million people were living with HIV, according to the World Health Organization.
HIV can be spread the following ways:
- By having unprotected sex with an infected partner; the virus can enter the body through the lining of the vagina, vulva, penis, rectum, or mouth during sex. Having a sexually transmitted disease (STD) such as syphilis, genital herpes, chlamydia, gonorrhea, or bacterial vaginosis appears to make people more susceptible to and at higher risk for acquiring HIV infection during sex with infected partners.
- By sharing needles or syringes (such as with intravenous injection drug abuse), which can be contaminated with very small quantities of blood from someone infected with the virus.
- HIV can be passed from mothers to their babies during pregnancy or childbirth. HIV also can be spread to babies through the breast milk of mothers infected with the virus. If the mother is treated with antiretroviral therapy (ART) during pregnancy, she can significantly reduce the chances of passing the infection to her baby.
- Through contact with infected blood; in the U.S. today, because of screening blood for transfusion and heat-treating techniques and other treatments of blood derivatives, the risk of getting HIV from transfusions is extremely small. However, before donated blood was screened for evidence of HIV infection and before treatments were introduced to destroy HIV in some blood products, such as factor VIII and albumin, HIV was transmitted through transfusion of contaminated blood or blood components. In areas of the world where donated blood is not routinely screened or treated for HIV, there is still risk of contracting the disease through this mode of transmission.
Initially, HIV usually causes flu-like symptoms, but some people may not experience any obvious signs or symptoms. The only way to determine whether you are infected is through HIV testing.
Your HIV status, like other medical conditions and test results, is protected by the Health Insurance Portability and Accountability Act (HIPAA) Privacy Rule and cannot be shared by healthcare providers with friends, family, or employers without written permission. However, if you test positive for HIV, it is important that you tell your healthcare providers as well as all sex partners and/or anyone with whom you share needles. Counseling services are often available from the clinic or healthcare provider that performed the test and they can help to advise you on who needs to know.
HIV status may be shared with healthcare providers who have a "need to know" in order to treat you. Also, in order to determine the incidence of HIV and to provide appropriate prevention and care services, all new cases of HIV are reported to state and local health departments.
Development of AIDS
- HIV may initially cause no symptoms or cause an acute illness with non-specific, flu-like symptoms that resolve after a week or two.
- During the first few weeks following infection with HIV, the virus infects T-cells, making numerous copies of itself and continuing to infect more T-cells. The virus is present in large numbers and is carried throughout the body.
- About 2 to 8 weeks after exposure, the immune system responds by producing antibodies against the virus.
- As HIV infects CD4 T-cells, it slowly begins to decrease their numbers.
- You may be apparently healthy for a decade or more, but without treatment, HIV continues to replicate and destroy CD4 T-cells that normally help the body fight infections. The virus remains in places such as the brain and lymph nodes, where it will persist even during drug treatment.
If you become infected with HIV and it is not detected early and treated, it may become a simmering infection that may cause few symptoms for a decade or more. If your infection is still not treated, eventually symptoms of AIDS emerge and begin to progressively worsen. Over time and without treatment, HIV destroys the immune system and your body’s ability to fight infections and certain cancers, leaving your body vulnerable to other debilitating diseases.
The term AIDS applies to the most advanced stages of HIV infection. According to the CDC, AIDS is diagnosed when the CD4 T-cell count drops below 200 cells/mm3. AIDS is also diagnosed when you have HIV and an AIDS-related illness, such as tuberculosis or pneumonia caused by Pneumocystis jirovecii (formerly called Pneumocystis carinii) a type of bacteria. In people with AIDS, opportunistic infections are often severe and sometimes fatal because the immune system is so damaged by HIV that the body cannot fight off certain bacteria, viruses, fungi, or parasites. Those with HIV/AIDS are also at an increased risk of developing certain cancers, neurological disorders, and a variety of other conditions.