HIV (human immunodeficiency virus) is a virus that damages the cells in your immune system and weakens your ability to fight everyday infections and disease.
AIDS (acquired immune deficiency syndrome) is the name used to describe a number of potentially life-threatening infections and illnesses that happen when your immune system has been severely damaged by the HIV virus.
While AIDS can't be transmitted from one person to another, the HIV virus can.
There's currently no cure for HIV, but there are very effective drug treatments that enable most people with the virus to live a long and healthy life.
With an early diagnosis and effective treatments, most people with HIV won't develop any AIDS-related illnesses and will live a near-normal lifespan.
These pages cover:
Most people experience a short, flu-like illness 2-6 weeks after HIV infection, which lasts for a week or two.
After these symptoms disappear, HIV may not cause any symptoms for many years, although the virus continues to damage your immune system. This means many people with HIV don't know they're infected.
Anyone who thinks they could have HIV should get tested. Certain groups of people are advised to have regular tests as they're at particularly high risk, including:
Read about symptoms of HIV.
HIV is found in the body fluids of an infected person. This includes semen, vaginal and anal fluids, blood, and breast milk.
It's a fragile virus and doesn't survive outside the body for long. HIV can't be transmitted through sweat, urine or saliva.
The most common way of getting HIV in the UK is through having anal or vaginal sex without a condom.
Other ways of getting HIV include:
The chance of getting HIV through oral sex is very low and will be dependent on many things, such as whether you receive or give oral sex and the oral hygiene of the person giving the oral sex.
Read about what causes HIV.
Seek medical advice as soon as possible if you think you might have been exposed to HIV.
You can get tested in a number of places, including at your GP surgery, sexual health clinics, and clinics run by charities.
The only way to find out if you have HIV is to have an HIV test. This involves testing a sample of your blood or saliva for signs of the infection.
It's important to be aware that:
If your first test suggests you have HIV, a further blood test will need to be carried out to confirm the result.
If this is positive, you'll be referred to a specialist HIV clinic for some more tests and a discussion about your treatment options.
Read about diagnosing HIV.
Antiretroviral medications are used to treat HIV. They work by stopping the virus replicating in the body, allowing the immune system to repair itself and preventing further damage.
These come in the form of tablets, which need to be taken every day.
HIV is able to develop resistance to a single HIV drug very easily, but taking a combination of different drugs makes this much less likely.
Most people with HIV take a combination of drugs – it's vital these are taken every day as recommended by your doctor.
The goal of HIV treatment is to have an undetectable viral load. This means the level of HIV virus in your body is low enough to not be detected by a test.
Read about treating HIV.
If you're living with HIV, taking effective HIV treatment and being undetectable significantly reduces your risk of passing HIV on to others.
You'll also be encouraged to:
Without treatment, the immune system will become severely damaged, and life-threatening illnesses such as cancer and severe infections can occur.
It's rare for a pregnant woman living with HIV to transmit it to her baby, provided she receives timely and effective HIV treatment and medical care.
Read about living with HIV.
Anyone who has sex without a condom or shares needles is at risk of HIV infection.
Knowing your HIV status and that of your partner is also important.
For people with HIV, taking effective HIV treatment and being undetectable significantly reduces the risk of passing HIV on to others.
Read about preventing HIV.