HIV is a virus which attacks the immune system, and weakens your ability to fight infections and disease. It's most commonly caught by having sex without a condom.

It can also be passed on by sharing infected needles and other injecting equipment, and from an HIV-positive mother to her child during pregnancy, birth and breastfeeding.

HIV stands for human immunodeficiency virus. The virus attacks the immune system, and weakens your ability to fight infections and disease.

There is no cure for HIV, but there are treatments to enable most people with the virus to live a long and healthy life.

AIDS is the final stage of HIV infection, when your body can no longer fight life-threatening infections. With early diagnosis and effective treatment, most people with HIV will not go on to develop AIDS.

How do you get HIV?

HIV is found in the body fluids of an infected person, which includes semen, vaginal and anal fluids, blood, and breast milk. It is a fragile virus and does not survive outside the body for long. 

HIV cannot be transmitted through sweat or urine.

The most common way of getting HIV in the UK is by anal or vaginal sex without a condom. According to statistics from Public Health England, 95% of those diagnosed with HIV in the UK in 2013 acquired HIV as a result of sexual contact.

Other ways of getting HIV include:

  • using a contaminated needle, syringe or other injecting equipment
  • tranmission from mother to baby during pregnancy, birth or breastfeeding
  • through oral sex or sharing sex toys (although the risk is significantly lower than for anal and vaginal sex) 

How common is HIV?

At the end of 2013, there were an estimated 107,800 people in the UK living with HIV. The majority were infected through sex (43,500 gay and bisexual men and 59,500 heterosexuals).

A quarter of people with HIV (over 26,100) do not know they are infected.

Around one in every 360 people in the UK has HIV, but the two groups with highest rates of HIV are gay and bisexual men and Black African heterosexuals, where the rates are approximately one in 17 and one in 18 respectively.

The World Health Organization estimates that around 35 million people in the world are living with HIV.

The virus is more common in sub-Saharan African countries, such as South Africa, Zimbabwe and Mozambique.


Symptoms of HIV 

Most people who are infected with HIV experience a short, flu-like illness that occurs two to six weeks after infection. After this, HIV often causes no symptoms for several years.

The flu-like illness that often occurs a few weeks after HIV infection is also known as seroconversion illness. It's estimated that up to 80% of people who are infected with HIV experience this illness.

The most common symptoms are:

  • fever (raised temperature)
  • sore throat
  • body rash

Other symptoms can include:

  • tiredness
  • joint pain
  • muscle pain
  • swollen glands (nodes)

The symptoms usually last one to two weeks but can be longer. They are a sign that your immune system is putting up a fight against the virus. 

However, these symptoms are most commonly caused by conditions other than HIV, and do not mean you have the virus.

If you have several of these symptoms, and you think you have been at risk of HIV infection within the past few weeks, you should get an HIV test.

After the initial symptoms disappear, HIV will often not cause any further symptoms for many years. During this time, known as asymptomatic HIV infection, the virus continues to be active and causes progressive damage to your immune system. This process can take about 10 years, during which you will feel and appear well.

Once the immune system becomes severely damaged symptoms can include:

  • weight loss
  • chronic diarrhoea
  • night sweats
  • skin problems
  • recurrent infections
  • serious life-threatening illnesses

Earlier diagnosis and treatment of HIV can prevent these problems.


Treating HIV 

There is no cure for HIV, but there are treatments to enable most people with the virus to live a long and healthy life.

Emergency HIV drugs

If you think you have been exposed to the virus within the last 72 hours (three days), anti-HIV medication may stop you becoming infected.

For it to be effective, the medication, called post-exposure prophylaxis or PEP, must be started within 72 hours of coming into contact with the virus. It is only recommended following higher risk exposure, particularly where the sexual partner is known to be positive.

The quicker PEP is started the better, ideally within hours of coming into contact with HIV. The longer the wait, the less chance of it being effective.

PEP has been misleadingly popularised as a “morning-after pill” for HIV – a reference to the emergency pill women can take to prevent getting pregnant after having unprotected sex.

But the description is not accurate. PEP is a month-long treatment, which may have serious side effects and is not guaranteed to work. The treatment involves taking the same drugs prescribed to people who have tested positive for HIV.

You should be able to get PEP from:

  • sexual health clinics, or genitourinary medicine (GUM) clinics
  • hospitals – usually accident and emergency (A&E) departments

If you already have HIV, try your HIV clinic if the PEP is for someone you've had sex with.

If you test positive

If you are diagnosed with HIV, you will have regular blood tests to monitor the progress of the HIV infection before starting treatment.

This involves monitoring the amount of virus in your blood (viral blood test) and the effect HIV is having on your immune system. This is determined by measuring your levels of CD4+ve lymphocyte cells in your blood. These cells are important for fighting infection. 

Treatment is usually recommended to begin when your CD4 cell count falls towards 350 or below, whether or not you have any symptoms. In some people with other medical conditions, treatment may be started at higher CD4 cell counts. When to start treatment should be discussed with your doctor.

The aim of the treatment is to reduce the level of HIV in the blood, allow the immune system to repair itself and prevent any HIV-related illnesses.

If you are on HIV treatment, the level of the virus in your blood is generally very low and it is unlikely that you will pass HIV on to someone else.

If you have another condition

If you have also been diagnosed with hepatitis B or hepatitis C, it is recommended that you start treatment when your CD4 count falls below 500.

Treatment is recommended to begin at any CD4 count if you are on radiotherapy or chemotherapy that will suppress your immune system, or if you have been diagnosed with certain other illnesses, including:

  • tuberculosis
  • HIV-related nephropathy (kidney disease)
  • HIV-related neurocognitive (brain) illnesses

Want to know more?

  • nam (aidsmap.com): Starting treatment if you have another condition

Antiretroviral drugs

HIV is treated with antiretrovirals (ARVs), these work by stopping the virus replicating in the body, allowing the immune system to repair itself and preventing further damage.

A combination of ARVs is used because HIV can quickly adapt and become resistant to one single ARV.

Patients tend to take three or more types of ARV medication. This is known as combination therapy or antiretroviral therapy (ART).

Some antiretroviral drugs have been combined into one pill, known as a "fixed dose combination". This means that the most common treatments for people just diagnosed with HIV involve taking just one or two pills a day.

Different combinations of ARVs work for different people so the medicine you take will be individual to you.

Once HIV treatment is started, you will probably need to take the medication for the rest of your life. For the treatment to be continuously effective, it will need to be taken regularly every day. Not taking ARVs regularly may cause the treatment to fail.

Many of the medicines used to treat HIV can interact with other medications prescribed by your GP or bought over-the-counter. These include herbal remedies such as St John's Wort, as well as recreational drugs.

Always check with your HIV clinic staff or your GP before taking any other medicines.

Pregnancy

ARV treatment is available to prevent a pregnant woman from passing HIV to her child.

Without treatment, there is a one in four chance your baby will become infected with HIV. With treatment, the risk is less than one in 100.

Advances in treatment mean there is no increased risk of passing the virus to your baby with a normal delivery. However, for some women, a caesarean section may still be recommended.

If you have HIV, do not breastfeed your baby because the virus can be transmitted through breast milk.

If you or your partner has HIV, speak to an HIV doctor as there are options for safely conceiving a child without putting either of you at risk of infection.

Missing a dose

HIV treatment only works if you take your pills regularly every day. Missing even a few doses will increase the risk of your treatment not working.

You will need to develop a daily routine to fit your treatment plan around your lifestyle.

Side effects

HIV treatment can have side effects. If you get serious side effects (which is uncommon) you may need to try a different combination of ARVs.

Common side effects include:

  • nausea
  • diarrhoea
  • skin rashes
  • sleep difficulties

Preventing HIV 

The main way to prevent HIV infection is to reduce the risk of exposure to HIV, such as having sex without a condom and sharing needles and other injecting equipment.

If you have HIV you can pass it on to others if you have sex without a condom, or share needles, syringes, or other injecting equipment. HIV treatment with ART substantially reduces the risk of passing the virus onto someone else.

Knowing your HIV status and that of your partner is important and if you are at regular risk of potential exposure to HIV you should have a regular HIV test.

Sex

HIV can be transmitted by having vaginal or anal sex without a condom. There is also a risk of transmission through oral sex, but this risk is much lower. 

HIV can also be caught from sharing sex toys with someone infected with HIV.

See causes of HIV for more on transmission of HIV.

The best way to prevent HIV and other sexually transmitted infections (STIs) is to use a condom for penetrative sex and a dental dam for oral sex.

Condoms

Condoms come in a variety of shapes, colours, textures, materials and flavours. Both male and female condoms are available.

A condom is the most effective form of protection against HIV and other STIs. It can be used for vaginal and anal sex, and for oral sex performed on men.

HIV can be passed on before ejaculation, through pre-come and vaginal secretions, and from the anus.

It is very important that condoms are put on before any sexual contact occurs between the penis, vagina, mouth or anus.

Lubricant

Lubricant, or lube, is often used to enhance sexual pleasure and safety, by adding moisture to either the vagina or anus during sex.

Lubricant can make sex safer by reducing the risk of vaginal or anal tears caused by dryness or friction, and it can also prevent a condom from tearing.

Only water-based lubricant (such as K-Y Jelly) rather than an oil-based lubricant (such as Vaseline or massage and baby oil) should be used with condoms.

Oil-based lubricants weaken the latex in condoms and can cause them to break or tear.

Dental dams

A dental dam is a small sheet of latex that works as a barrier between the mouth and the vagina or anus to reduce the risk of STIs during oral sex.

Sharing needles and injecting equipment

If you inject drugs, don't share needles or syringes, or other injecting equipment such as spoons and swabs, as this could expose you to HIV and other viruses found in the blood, such as hepatitis C.

Many local authorities and pharmacies offer needle exchange programmes, where used needles can be exchanged for clean ones.

If you are a heroin user, consider enrolling in a methadone programme. Methadone can be taken as a liquid, so it reduces your risk of getting HIV.

A GP or drug counsellor should be able to advise you about both needle exchange programmes and methadone programmes.

If you are having a tattoo or piercing, it's important that a clean, sterilised needle is always used.