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Key points

  • Human immunodeficiency virus (HIV) is a virus that attacks your immune system.
  • Acquired immune deficiency syndrome (AIDS) is when your immune system is weakened so much by HIV that it can't fight life-threatening infections.
  • There isn’t a cure for HIV but it can be controlled with medicines.
  • You can greatly reduce the risk of catching or passing on HIV by always using a condom when you have sex.

Human immunodeficiency virus (HIV) is a virus that attacks your immune system and increases your risk of infection, serious illnesses and some types of cancer. Acquired immune deficiency syndrome (AIDS) is when your immune system is weakened so much by HIV that it can't fight life-threatening infections and illnesses.


Around 96,000 people were estimated to be living with HIV in the UK at the end of 2011. About a quarter of these people were thought to be unaware they had been infected.

The majority of HIV infections are in heterosexual people, usually people who have come to live in the UK from countries where HIV is widespread. However, it’s possible to get infected with HIV in the UK. Infections are common among men who have sex with men.

Although there isn’t a cure for HIV, it can often be effectively controlled with treatment. Most people who have it can live healthy and productive lives.

The immune system

When your immune system is healthy, it defends your body against bacteria, viruses and other infections. White blood cells find and destroy things that your body sees as 'foreign' and this stops you developing serious diseases.

HIV avoids being detected and destroyed by your immune system by changing its outer 'coat' again and again. It multiplies (replicates) inside a type of white blood cell called a CD4 cell. This kind of cell is normally involved in helping to attack and destroy bacteria and viruses.

As HIV multiplies, it destroys the CD4 cells in your body, so there are fewer of them. This means that your body's ability to fight other infections is weakened and your defences against certain cancers are reduced.

Symptoms of HIV/AIDS

Primary HIV infection

Most people who get HIV don't have any symptoms in the first years after being infected. Some people develop symptoms between one and six weeks after being infected with HIV, which are similar to flu. This is known as primary HIV infection. Symptoms of primary HIV include:

  • fever
  • swollen glands
  • sore throat
  • a rash on your body
  • painful muscles or joints
  • a headache

If you have any of these symptoms and think you may have been infected with HIV, see your GP or visit a sexual health clinic.

During this time, you're very infectious because the amount of the virus in your blood is high. Therefore, the risk of passing the infection on to someone else is also high.

The symptoms of a primary HIV infection usually last for a week to a month and then, for most people, they go. You might not have any further symptoms of HIV for years – some people don't have any for 12 years or more. This phase is called asymptomatic HIV infection.

Symptomatic HIV infection

After a period of time you may start to get symptoms again. You may be more prone to getting skin infections, such as warts or fungal infections. Other symptoms may include:

  • a fever
  • weight loss
  • night sweats
  • persistent diarrhoea

Advanced HIV infection (AIDS)

Without treatment, most people will go on to develop advanced HIV infection (AIDS). Eventually, you could be at risk of life-threatening illnesses that include:

Causes of HIV/AIDS

Most people with HIV become infected when they have unprotected vaginal or anal sex. Not everyone who is exposed to HIV will be infected with the virus. However, it’s more likely if you have repeated sexual contact with someone who has HIV. There is a small chance of getting infected through unprotected oral sex. It’s particularly risky if you have mouth ulcers or gum disease, and your partner ejaculates in your mouth.

HIV can also be passed on through direct contact with infected blood. For example, if you use infected needles to inject drugs, do piercings or tattoos. If you're a healthcare worker, you can potentially get HIV from an accidental injury with a needle contaminated with infected blood.

If you're pregnant and have HIV, you can pass on the virus to your baby during your pregnancy, when you give birth or when breastfeeding. However, you can prevent this if you take HIV medicines and bottle feed your baby instead of breastfeeding.

In the past, some people were infected with HIV through blood or organ donations. All donations in the UK are now screened for HIV, so the chance of this happening is extremely low.

Other fluids in your body, such as saliva, sweat or urine, don’t contain high enough levels of HIV to cause an infection. HIV can't be passed on through normal day-to-day activities, such as sharing cutlery, sitting on toilet seats or by shaking hands. And it can't be passed on through a mosquito bite or bites from other animals or insects.

Diagnosis of HIV/AIDS

If you think you may have been infected with HIV, it's important to see your GP or visit a sexual health clinic.

Your GP will ask about your symptoms and examine you. He or she may also ask you about your medical and sexual history.

You will need to have a blood test to check for HIV antibodies (proteins produced by your immune system that fight against the virus). This can be in the form of a rapid finger prick test, which means you get the results very quickly. Alternatively, or if a finger prick test is positive, you may have a sample of blood taken from your arm. This is then sent to a laboratory for testing.

It can take up to three months for HIV to show in your blood so you may need to have the test again.

Treatment of HIV/AIDS

There is no cure for HIV infection. However, life-long treatment with anti-HIV medicines can stop further damage to your immune system and allow it to restore itself over a period of years. If you take anti-HIV medicines consistently, they will enable you to stay well and live a full life.

HIV treatment is managed at specialist outpatient clinics and it's important to attend all your appointments. At these appointments your health professional will check how well your immune system is working and ask you about your general health.

You probably won’t need to start treatment until your number of CD4 white blood cells has fallen to a low level (350 or lower). You may be advised to start treatment sooner if you develop a serious infection or condition linked to advanced HIV infection, or get pregnant.


Medicines for HIV work in a number of different ways. For this reason, you usually take a combination of medicines together. This is known as antiretroviral therapy, combination therapy or highly active antiretroviral therapy (HAART). The medicines will prevent HIV from reproducing in your body and reduce the amount of virus in your blood. This will allow your immune system to recover.

Combination therapies usually use medicines that attack the virus at different stages of its life cycle. Your doctor will give you advice about the best medicines for you. It's very important to take your medicine regularly, otherwise the virus can become resistant to it and the medicine will no longer be effective.

Always ask your doctor for advice and read the patient information leaflet that comes with your medicine.


You may develop side-effects in the first few months after you start your treatment. These are the unwanted effects you may get after taking a medicine. If you have side-effects, it's important to talk to the doctor who prescribed your medicine before you stop taking it. Side-effects of HIV medicines may include:

  • feeling or being sick
  • diarrhoea or wind
  • feeling tired
  • aching muscles
  • a rash
  • having trouble sleeping or bad dreams
  • dizziness

These side-effects should improve as your body gets used to the medicine. If they don’t, see your doctor to discuss other treatment options.

Certain HIV medicines can increase your risk of serious conditions, such as heart disease by causing high levels of cholesterol (fats) in your blood. Therefore, it’s important to see your doctor regularly so that any side-effects can be monitored. Some side-effects can be controlled with other medicines.

Prevention of HIV/AIDS

You can greatly reduce the risk of getting or passing on HIV by always using a condom when you have sex (including oral sex). However, condoms can't completely eliminate the risk of HIV infection.

If you reduce the number of partners you have sex with, it will reduce your overall risk of getting infected with HIV. It's a good idea to have regular checks for sexually transmitted infections (STIs) too.

If you take intravenous drugs or inject medicines, don't share injection equipment and always use a fresh needle.

Post-exposure prophylaxis treatment

Post-exposure prophylaxis (PEP) is an emergency medicine treatment, which can reduce your chance of getting infected if you’re exposed to HIV. For example, you may be exposed if a condom breaks or if you’re a healthcare worker exposed to HIV. If you suspect you have been exposed to HIV, seek urgent medical attention.

For more information about PEP, see our frequently asked questions.

Reviewed by Rachael Mayfield-Blake, Bupa Health Information Team, March 2014.

Find out more about our health editors.

For answers to frequently asked questions about this topic, see FAQs.

For sources and links to further information, see Resources.

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  • This information was published by Bupa's Health Information Team and is based on reputable sources of medical evidence. It has been reviewed by appropriate medical or clinical professionals. Photos are only for illustrative purposes and do not reflect every presentation of a condition. The content is intended only for general information and does not replace the need for personal advice from a qualified health professional. For more details on how we produce our content and its sources, visit the about our health information page.

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