DefinitionHIV infection is a condition caused by the human immunodeficiency virus (HIV). The condition gradually destroys the immune system, which makes it harder for the body to fight infections.This article provides a general overview. For more detailed information, see:AIDSAcute HIV infectionAsymptomatic HIV infectionEarly symptomatic HIV infectionAlternative NamesHuman immunodeficiency virus infectionCauses, incidence, and risk factorsThe human immunodeficiency virus (HIV) can be spread by the following:Through sexual contact — including oral, vaginal, and anal sexThrough blood — through blood transfusions, accidental needlesticks, or needle sharingFrom mother to child — a pregnant woman can transmit the virus to her fetus through their shared blood circulation, or a nursing mother can pass it to her baby in her breast milkRare ways the virus may be spreadinclude:Accidental needle injuryArtificial insemination with infected semenOrgan transplantation with infected organsBlood banks and orang donor programs screen donors, blood, and tissues thoroughly to prevent the risk of infection. HIV is NOT transmitted to a person who DONATES blood or organs. People who donate organs are never in direct contact with people who receive them. Likewise, a person who donates blood is never in contact with the person receiving it. In all these procedures, sterile needles and instruments are used.HIV infection is NOT spread by:Casual contact such as huggingMosquitoesParticipation in sportsTouching items that were touched by a person infected with the virusPeople at highest risk for getting HIV include:Injection drug users who share needlesInfants born to mothers with HIV who didnt receive HIV therapy during pregnancyPeoplewho haveunprotected sex, especially with people who have other high-risk behaviors, are HIV-positive, or have AIDSPeople who received blood transfusions or clotting products between 1977 and 1985 (before screening for the virus became standard practice)Sexual partners of those who participate in high-risk activities (such as injection drug use or anal sex)See also: AIDSadvertisementSymptomsPeople who become infected with HIV may not have any symptoms for up to 10 years, but they can still pass the infection to others. After you come in contact with the virus, it can take up to 3 months for a blood test to show that you have HIV.Symptoms related to HIV are usually due to a different infection in the body. Some symptoms related to HIV infection include:DiarrheaFatigueFeverFrequent vaginal yeast infectionsHeadacheMouth sores, including yeast infection (thrush)Muscle stiffness or achingRashes of different types, including seborrheic dermatitis and psoriasisSore throatSwollen lymph glandsNote: Many people have no symptoms when they are diagnosed with HIV.Signs and testsThe HIV ELISA and HIV Western blot tests detect antibodies to the HIV virus in the blood. Both tests must be positive to confirm an HIV infection. Having these antibodies means you are infected with HIV.If the test is negative (no antibodies found) and you have risk factors for HIV infection, you should be retested in 3 months.If the HIV ELISA and HIV Western blot tests are positive, other blood tests can be done to determine how much HIV is in your bloodstream.A complete blood count (CBC) and white blood cell differential may also show abnormalities.A lower-than-normal CD4 cell count may be a sign that the virus is damaging your immune system.TreatmentDoctors usually recommend medicine for patients who are committed to taking all their medications and have a CD4 count below 500 cells/mm3 (which is a sign that of a weakened immune system). Some people, including pregnant women and people with kidney or neurological problems related to HIV, may need treatment regardless of their CD4 count.It is extremely important for people with HIV to take all doses of their medications, otherwise the virus may become resistant to the drugs. Therapy always involves a combination of antiviral drugs. Pregnant women with HIV infection are treated to reduce the chance of transmitting HIV to their babies.People with HIV infection need to become educated about the disease and treatment so that they can be active participants in making decisions with their health care provider.Support GroupsSee: AIDS – support groupExpectations (prognosis)HIV is a chronic medical condition that can be treated, but not yet cured. There are effective ways to prevent complications and delay, but not always prevent, progression to AIDS.Almost all people infected with HIV will develop AIDS if not treated. However, there is a small group of people who develop AIDS very slowly, or never at all. These patients are called long-term nonprogressors.ComplicationsCancersChronic wasting (weight loss) from HIV infectionHIV dementiaHIV lipodystrophyOpportunistic infectionsBacillary angiomatosisCandidiasisCytomegalovirus infectionCryptococcal infectionCryptosporidium enterocolitis (or other protozoal infections)Mycobacterium avium complex (MAC) infectionPneumocystis jiroveci pneumonia (previously called Pneumocystis carinii pneumonia or PCP)Salmonella infection in the bloodstreamToxoplasmosisTuberculosis (in the lungs or spread throughout the body)Viral infection of the brain (progressive multifocal leukoencephalopathy)Calling your health care provideradvertisementCall your health care provider if you have had a possible or actual exposure to AIDS or HIV infection.PreventionAvoid injecting illicit drugs. If you use injected drugs, avoid sharing needles or syringes. Always use new needles. (Boiling or cleaning them with alcohol does not guarantee that theyre sterile and safe.)Avoid oral, vaginal, or anal contact with semen from HIV-infected people.Avoid unprotected anal intercourse, since it causes small tears in the rectal tissues, through which HIV in an infected partners semen may enter directly into the other partners blood.If you have sex with people who use injected drugs, always use condoms.If you have sex with many people or with people who have multiple partners, always use condoms.People with AIDS or who have had positive HIV antibody tests can pass the disease on to others. They should not donate blood, plasma, body organs, or sperm. They should not exchange genital fluids during sexual activity.Safer sex behaviors may reduce the risk of getting the infection. There is still a slight risk of getting the infection even if you practice “safe sex” by using condoms. Abstinence is the only sure way to prevent sexual transmission of the virus.Use protection when having sexual contact with people you know or suspect of being infected with HIV. Even better, use protection for ALL sexual contact.ReferencesQuinn TC. Epidemiology of human immunodeficiency virus infection and acquired immunodeficiency syndrome. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 392.Sterling TR, Chaisson RE. General clinical manifestations of human immunodeficiency virus infection (including the acute retroviral syndrome and oral, cutaenous, renal, ocular, metabolic, and cardiac diseases. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2009:chap 121.Review Date:5/30/2012Reviewed By:David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.