What is HIV?

Human immunodeficiency virus (HIV) is a disease that attacks your immune system, making it harder for your body to fight off infections. The virus is carried in the blood and bodily fluids of an infected person and can be passed on through unprotected sex, which is why it is classed as a sexually transmitted infection (STI).

If left untreated for many years HIV can cause acquired immune deficiency syndrome (AIDS). This is where the immune system becomes severely damaged, and common infections become life-threatening.

There is no cure for HIV, but with early diagnosis and the correct treatment you can live a long and healthy life.

How do you get HIV?

HIV is spread through infected bodily fluids. Most people contract HIV by having vaginal or anal sex without a condom. It can also be spread on unwashed sex toys. Less commonly, HIV can be transmitted through oral sex.


After being infected with HIV, most people experience a short illness similar to the flu with these symptoms:

  • Fever
  • Sore throat
  • Rash
  • Tiredness
  • Aches and pains
  • Swollen glands

These symptoms do not necessarily indicate HIV, but if you think you may have been exposed to the virus, it’s a good idea to get tested.


If you think you’ve been exposed to HIV you should get tested as soon as possible. You can get an HIV test for free at a sexual health or GUM clinic, or at a Terrence Higgins Trust centre. Alternatively you can order a home test kit or visit a private clinic.

An HIV test requires a blood or saliva sample. You may need to have more than one HIV test to confirm the diagnosis.


If you think you’ve been exposed to HIV within the past 72 hours you may be able to prevent infection by taking emergency treatment known as post-exposure prophylaxis, or PEP.

Once you have been infected with HIV, treatment involves monitoring the amount of the virus in your blood (your “viral load”) and how much damage has been done to your immune system. At a certain point you will start taking antiretroviral medication, which stops the virus replicating.

Patients who are diagnosed early and take their medicine correctly usually reach an undetectable viral load – this is where HIV can no longer be detected in the blood, which means it cannot damage your immune system and is impossible to pass on.

Content reviewed by Jemma Shafier, a Doctor Care Anywhere GP