HIV and AIDS: How HIV Progresses to AIDS

The difference between HIV and AIDS

HIV is a virus. Once it enters the body, it infects CD4 T cells, the white blood cells that coordinate immune responses, and uses them to make copies of itself. For an overview of how HIV spreads, testing and prevention, see HIV infection.

AIDS is a stage of illness, not a separate infection. It describes the point at which HIV has destroyed so many CD4 cells that the immune system can no longer fight off infections and cancers that a healthy body controls easily. In the US, it is formally called stage 3 HIV.

How HIV progresses to AIDS

1. Acute HIV (stage 1): 2 to 4 weeks after infection, many people have a flu-like illness with fever, sore throat, rash and swollen glands. Viral levels are very high.
2. Chronic HIV (stage 2): the virus multiplies at lower levels. People often feel well for years, but CD4 cells fall steadily, on average by about 50 to 100 cells/mm³ a year. A normal CD4 count is about 500 to 1,500.
3. AIDS (stage 3): when the CD4 count drops below 200, or an AIDS-defining illness appears.

Without treatment, the time from infection to AIDS averages about 10 years but varies widely. Untreated, people with AIDS typically survive around 3 years, or about a year after a serious opportunistic infection.

The World Health Organization also uses the term advanced HIV disease for a CD4 count under 200, any WHO stage 3 or 4 condition, or any child under 5 with HIV. This group has the highest risk of death and needs a specific package of care.

AIDS-defining illnesses

These are infections and cancers that rarely cause serious disease in people with healthy immune systems. Diagnosis of one of them in someone with HIV means AIDS, whatever the CD4 count. The most important include:

Symptoms of AIDS

Symptoms come mainly from the infections and cancers that take hold:

• rapid, unexplained weight loss
• fevers and drenching night sweats lasting weeks
• extreme tiredness
• diarrhea lasting more than a week
• sores or white patches in the mouth, throat or genitals (thrush)
• persistent cough or breathlessness
• swollen lymph glands in the neck, armpits or groin
• red, brown, pink or purple blotches on or under the skin or in the mouth
• memory loss, confusion and depression

Diagnosis

• HIV test: a combined antigen/antibody blood test, confirmed with further testing.
• CD4 count: shows how much immune damage has occurred. Under 200 defines AIDS.
• HIV viral load: measures how much virus is in the blood and whether treatment is working.
• Resistance testing: guides the choice of antiretroviral drugs.
• Screening for infections: including TB, cryptococcal antigen when CD4 is under 100, hepatitis B and C, syphilis and toxoplasma antibodies.

Many people in the US are still first diagnosed with HIV at the AIDS stage, because they never tested. Routine testing at least once for everyone aged 13 to 64 is recommended by the CDC, and more often for people at higher risk.

Treatment

Antiretroviral therapy (ART)

ART is a combination of HIV medicines, often one pill a day. It stops the virus from multiplying, lets CD4 cells recover and prevents new opportunistic infections. ART should start as soon as possible after diagnosis, usually within days. For people with certain infections, such as cryptococcal or TB meningitis, ART is delayed for a few weeks to reduce dangerous inflammation.

Treating and preventing opportunistic infections

• Each active infection or cancer is treated directly.
• Preventive antibiotics: trimethoprim-sulfamethoxazole when CD4 is under 200 protects against PCP and toxoplasmosis.
• TB preventive therapy for people with latent TB.
• Vaccines: pneumococcal, hepatitis B, flu, COVID-19 and HPV. Live vaccines are avoided when CD4 is very low.

Preventive medicines can usually be stopped once ART has kept the CD4 count above 200 for several months.

Immune reconstitution inflammatory syndrome (IRIS)

As the immune system recovers on ART, it can react strongly to infections already in the body, causing fever, swollen glands or worsening symptoms in the first weeks to months. It is a sign the immune system is waking up. It is managed by continuing ART and sometimes adding steroids.

Outlook

AIDS is no longer a death sentence. On effective ART, CD4 counts usually rise over months to years, opportunistic infections become rare, and a person who started treatment with AIDS is no longer immunosuppressed once their counts recover. Many people diagnosed with HIV today and treated early have a life expectancy close to the general population. People who stay on treatment with an undetectable viral load also cannot pass HIV on through sex (undetectable equals untransmittable, or U=U).

Prevention

• Get tested, and treat HIV early to prevent AIDS.
• Use condoms, and take PrEP (daily pills or long-acting injections) if you are at higher risk.
• Seek PEP within 72 hours of a possible exposure.
• Never share needles or injection equipment.
• Pregnant people with HIV on ART rarely pass HIV to their baby.

Frequently asked questions

What is the difference between HIV and AIDS?

HIV is the virus that damages the immune system. AIDS is the most advanced stage of untreated HIV infection, defined by a CD4 count under 200 or an AIDS-defining illness. Everyone with AIDS has HIV, but most people with HIV, especially on treatment, never develop AIDS.

How long does it take HIV to turn into AIDS?

Without treatment, it usually takes around 8 to 10 years, though it can happen within 2 to 3 years in some people and take longer in others. With antiretroviral therapy started early, HIV usually never progresses to AIDS.

Can AIDS be reversed?

The immune damage of AIDS can largely recover. With consistent ART, the virus is suppressed and CD4 counts often rise above 200 and higher over time. The HIV infection itself is not cured, so treatment must continue for life.

What CD4 count is AIDS?

A CD4 count below 200 cells/mm³ in someone with HIV meets the definition of AIDS. A normal count in a healthy adult is roughly 500 to 1,500. AIDS is also diagnosed at any CD4 count if an AIDS-defining illness develops.

What is the life expectancy of someone with AIDS?

Without treatment, survival after an AIDS diagnosis is typically around 3 years. With ART, many people diagnosed with AIDS recover their immune system and can live for decades. Outcomes are best when treatment starts quickly and is taken every day.