How HIV spreads

To become infected with HIV, infected blood, semen or vaginal secretions must enter your body. This can happen in several ways:

• By having sex. You may become infected if you have vaginal, anal or oral sex with an infected partner whose blood, semen or vaginal secretions enter your body. The virus can enter your body through mouth sores or small tears that sometimes develop in the rectum or vagina during sexual activity.
• By sharing needles. Sharing contaminated injection drug paraphernalia (needles and syringes) puts you at high risk of HIV and other infectious diseases, such as hepatitis.
• From blood transfusions. In some cases, the virus may be transmitted through blood transfusions. Hospitals and blood banks screen the blood supply for HIV, so this risk is very small in the U.S. and other upper-middle-income countries. The risk may be higher in low-income countries that are not able to screen all donated blood.
• During pregnancy or delivery or through breastfeeding. Infected mothers can pass the virus on to their babies. Mothers who are HIV-positive and get treatment for the infection during pregnancy can significantly lower the risk to their babies.

How HIV doesn’t spread

You can’t become infected with HIV through ordinary contact. That means you can’t catch HIV or AIDS by hugging, kissing, dancing or shaking hands with someone who has the infection.

HIV isn’t spread through the air, water or insect bites.

Risk factors

Anyone of any age, race, sex or sexual orientation can be infected with HIV/AIDS. However, you’re at greatest risk of HIV/AIDS if you:

• Have unprotected sex. Use a new latex or polyurethane condom every time you have sex. Anal sex is riskier than is vaginal sex. Your risk of HIV increases if you have multiple sexual partners.
• Have an STI. Many STIs produce open sores on your genitals. These sores act as doorways for HIV to enter your body.
• Use illicit injection drugs. People who use illicit injection drugs often share needles and syringes. This exposes them to droplets of other people’s blood.

Complications

HIV infection weakens your immune system, making you much more likely to develop many infections and certain types of cancers.

Infections common to HIV/AIDS

• Pneumocystis pneumonia (PCP). This fungal infection can cause severe illness. Although it’s declined significantly with current treatments for HIV/AIDS, in the U.S., PCP is still the most common cause of pneumonia in people infected with HIV.
• Candidiasis (thrush). Candidiasis is a common HIV-related infection. It causes inflammation and a thick, white coating on your mouth, tongue, esophagus or vagina.
• Tuberculosis (TB). TB is a common opportunistic infection associated with HIV. Worldwide, TB is a leading cause of death among people with AIDS. It’s less common in the U.S. thanks to the wide use of HIV medications.
• Cytomegalovirus. This common herpes virus is transmitted in body fluids such as saliva, blood, urine, semen and breast milk. A healthy immune system inactivates the virus, and it remains dormant in your body. If your immune system weakens, the virus resurfaces — causing damage to your eyes, digestive tract, lungs or other organs.
• Cryptococcal meningitis. Meningitis is an inflammation of the membranes and fluid surrounding your brain and spinal cord (meninges). Cryptococcal meningitis is a common central nervous system infection associated with HIV, caused by a fungus found in soil.
• Toxoplasmosis. This potentially deadly infection is caused by Toxoplasma gondii, a parasite spread primarily by cats. Infected cats pass the parasites in their stools, which may then spread to other animals and humans. Toxoplasmosis can cause heart disease, and seizures occur when it spreads to the brain.

Cancers common to HIV/AIDS

• Lymphoma. This cancer starts in the white blood cells. The most common early sign is painless swelling of the lymph nodes in your neck, armpit or groin.
• Kaposi’s sarcoma. A tumor of the blood vessel walls, Kaposi’s sarcoma usually appears as pink, red or purple lesions on the skin and mouth. In people with darker skin, the lesions may look dark brown or black. Kaposi’s sarcoma can also affect the internal organs, including the digestive tract and lungs.
• HPV-related cancers. These are cancers caused by human papillomavirus (HPV) infection. They include anal, oral and cervical cancer.

Other complications

• Wasting syndrome. Untreated HIV/AIDS can cause significant weight loss, often accompanied by diarrhea, chronic weakness and fever.
• Neurological complications. HIV can cause neurological symptoms such as confusion, forgetfulness, depression, anxiety and difficulty walking. HIV-associated neurocognitive disorders (HAND) can range from mild symptoms of behavioral changes and reduced mental functioning to severe dementia causing weakness and inability to function.
• Kidney disease. HIV-associated nephropathy (HIVAN) is an inflammation of the tiny filters in your kidneys that remove excess fluid and wastes from your blood and pass them to your urine. It most often affects Black or Hispanic people.
• Liver disease. Liver disease is also a major complication, especially in people who also have hepatitis B or hepatitis C.

Prevention

There’s no vaccine to prevent HIV infection and no cure for HIV/AIDS. But you can protect yourself and others from infection.

To help prevent the spread of HIV:

• Consider preexposure prophylaxis (PrEP). The combination oral drugs emtricitabine plus tenofovir disoproxil fumarate (Truvada) and emtricitabine plus tenofovir alafenamide fumarate (Descovy) can reduce the risk of sexually transmitted HIV infection in people at very high risk. PrEP can reduce your risk of getting HIV from sex by about 99% and from injection drug use by at least 74%, according to the Centers for Disease Control and Prevention. Descovy hasn’t been studied in people who have receptive vaginal sex.

  The FDA recently approved cabotegravir (Apretude), the first injectable PrEP to reduce the risk of sexually transmitted HIV infection in people at very high risk. The injection is given by a health care provider. After the first two monthly injections, cabotegravir is given every two months. The injection is an option in place of a daily PrEP pill.

  Your health care provider will prescribe these drugs for HIV prevention only if you don’t already have HIV infection. You will need an HIV test before you start taking any PrEP. The test should then be done every three months for pills or before each injection for as long as you’re taking PrEP. Your health care provider will also test your kidney function before prescribing Truvada and continue to test it every 6 to 12 months. Other regular testing may also be needed.

  You need to take the pill form every day or closely follow the injection schedule for cabotegravir. They don’t prevent other STIs, so you’ll still need to practice safe sex. If you have hepatitis B, you should be evaluated by an infectious disease or liver specialist before beginning therapy.

• Use treatment as prevention (TasP). If you’re living with HIV, taking HIV medication can keep your partner from becoming infected with the virus. If you make sure your viral load stays undetectable — a blood test doesn’t show any virus — you won’t transmit the virus to anyone else through sex. Using TasP means taking your medication exactly as prescribed and getting regular checkups.
• Use post-exposure prophylaxis (PEP) if you’ve been exposed to HIV. If you think you’ve been exposed through sex, needles or in the workplace, contact your health care provider or go to the emergency department. Taking PEP as soon as possible within the first 72 hours can greatly reduce your risk of becoming infected with HIV. You will need to take medication for 28 days.
• Use a new condom every time you have sex. Use a new condom every time you have anal or vaginal sex. Women can use a female condom. If using a lubricant, make sure it’s water-based. Oil-based lubricants can weaken condoms and cause them to break. During oral sex use a nonlubricated, cut-open condom or a dental dam — a piece of medical-grade latex.
• Tell your sexual partners if you have HIV. It’s important to tell all your current and past sexual partners that you’re HIV-positive. They’ll need to be tested.
• Use a clean needle. If you use a needle to inject illicit drugs, make sure it’s sterile and don’t share it. Take advantage of needle-exchange programs in your community. Consider seeking help for your drug use.
• If you’re pregnant, get medical care right away. If you’re HIV-positive, you may pass the infection to your baby. But if you receive treatment during pregnancy, you can significantly cut your baby’s risk.
• Consider male circumcision. There’s evidence that male circumcision can help reduce the risk of getting HIV infection.