Scanning electron micrograph of HIV-1, coloured green, budding from a cultured lymphocyte

What are HIV and AIDS?

HIV- Human Immunodeficiency Virus

HIV attacks the body’s immune system gradually causing damage. Without treatment, the immune system will become too weak to fight off illness and infection.

There is currently no cure for HIV. But major advances in treatment mean that many people can lead long and healthy lives, although some may experience side effects from the treatment.

HIV is present in blood, genital fluids (semen, vaginal fluids and moisture in the rectum) and breast milk.

AIDS- Acquired Immune Deficiency Syndrome

AIDS is the term used to describe a stage of HIV infection when the body is too weak to fight off a range of diseases.

You cannot catch AIDS. HIV causes AIDS and it is HIV that can be passed on. Being diagnosed with AIDS means different things for different people.

Just because someone has AIDS does not mean they will die – but it is essential to have medical care and treatment.

The main ways HIV can be passed on

In the UK, most cases of HIV are caused by having sex with a person who has HIV without using a condom.

A person with HIV can pass the virus on to others even if they don't have any symptoms. People with HIV can pass the virus on more easily in the weeks following infection.

HIV treatment significantly reduces the risk of someone with HIV passing it on.

Sexual contact

Most people diagnosed with HIV in the UK acquire the virus through unprotected vaginal or anal sex.

It may also be possible to catch HIV through unprotected oral sex, but the risk is much lower.

The risk is higher if:

  • the person giving oral sex has mouth ulcers, sores or bleeding gums
  • the person receiving oral sex has recently been infected with HIV and has a lot of the virus in their body, or another sexually transmitted infection

Other risk behaviours

Other ways of getting HIV include:

  • sharing needles, syringes and other injecting equipment 
  • from mother to baby before or during birth or by breastfeeding
  • sharing sex toys with someone infected with HIV
  • healthcare workers accidentally pricking themselves with an infected needle, but this risk is extremely low
  • blood transfusion – now very rare in the UK, but still a problem in developing countries

How HIV is transmitted

HIV isn't easily passed on from one person to another. The virus doesn't spread through the air like cold and flu viruses.

HIV lives in the blood and in some body fluids. To get HIV, one of these fluids from someone with HIV has to get into your blood.

The body fluids that contain enough HIV to infect someone are:

  • semen
  • vaginal fluids, including menstrual blood
  • breast milk
  • blood
  • lining inside the anus

Other body fluids, like saliva, sweat or urine, don't contain enough of the virus to infect another person.

The main ways the virus enters the bloodstream are: 

  • by injecting into the bloodstream with needles or injecting equipment that's been shared with other people
  • through the thin lining on or inside the anus, vagina and genitals
  • through the thin lining of the mouth and eyes
  • through cuts and sores in the skin

But there are ways of preventing HIV infection in all of these situations.

HIV isn't passed on through:
  • spitting
  • kissing
  • being bitten
  • contact with unbroken, healthy skin
  • being sneezed on
  • sharing baths, towels or cutlery
  • using the same toilets or swimming pools
  • mouth-to-mouth resuscitation
  • contact with animals or insects like mosquitoes

Symptoms of HIV

These vary from person to person, People can live with HIV for years before having any symptoms. The only way to be sure if you have HIV is to have an HIV test. You cannot tell from symptoms alone.

Why take an HIV Test?

The sooner you’re diagnosed with HIV, the sooner you can start treatment.

Antiretroviral drugs(ARVs) will keep the virus under control by stopping it from reproducing itself. The goal is to keep levels of HIV so low that in tests the person has an undetectable viral load.

If someone with HIV is on effective treatment and has an undetectable viral load they cannot pass on HIV.

Find out more on the Terrence Higgins Trust (THT) website. Terrence Higgins Trust is the UK's leading HIV and sexual health charity.

There are now many quick and convenient ways to test for HIV

HIV tests are available in lots of healthcare settings. This might be in a sexual health clinic, doctor’s surgery, hospital or private clinic, for example. In many countries, there are also places where you can be tested in your local community.

In the UK, you can get a free and confidential HIV test at any NHS sexual health or GUM (genito-urinary medicine) clinic.

These clinics are linked into specialist HIV services, and there will be support available to you if your result is positive.

More information about HIV and how to get tested:

Terrence Higgins Trust

The UK's leading HIV and sexual health charity


UK-based charity providing accurate and trusted information about HIV and sexual health worldwide

NHS: Find testing services near you

An HIV test is the only way to know if you have HIV

Current treatment for HIV

Antiretroviral drugs cannot cure HIV but work by reducing the amount of HIV in the body so the immune system can work normally.

This doesn’t get rid of HIV completely, but with the right treatment and care, someone with HIV can expect to live a long and healthy life.

It is now recommended that everyone diagnosed with HIV starts treatment straight away.

Early diagnosis enables better treatment outcomes and reduces the risk of onward transmission.

People diagnosed late have a much higher risk of developing complex health conditions including HIV -associated brain impairment.

What is PrEP?

Pre-exposure prophylaxis (PrEP) is an HIV prevention strategy that uses antiretroviral drugs to protect people who do not have HIV but who are at high risk of contracting HIV.

To be effective, Prep must be taken regularly, as directed. It does not prevent other sexually transmitted infections.

What is PEP?

Post-exposure Prophylaxis (PEP) is a short-term treatment that stops HIV spreading through the  body.

It must be taken within 72 hours of possible exposure to HIV.

HIV-Associated Brain Impairment

Mildmay specialises in the treatment of HIV-Associated Neurocognitive Disorder, or HAND, impairment caused by HIV entering and affecting the brain.

This is a form of severe dementia which Mildmay is able to reverse in 85% of our patients, enabling them to return to independent living.

People with HAND often display symptoms that are very similar to dementia, such as memory loss, confusion, loss of a sense of self, difficulty in walking, speaking or carrying out every day tasks.

Mildmay’s specialised treatment, care and rehabilitation includes highly skilled medical and nursing care, treatment, rehabilitation and a combined range of therapies.

HIV in the UK*

London has the largest numbers of people living with HIV, but numbers are growing in every part of the UK.


Sub-Saharan Africa has the most serious HIV and AIDS epidemic in the world. In 2013, an estimated 24.7 million people were living with HIV, accounting for 71 per cent of the global total.

HIV Pregnancy and Birth**

In the UK with the right treatment and care, 99 per cent of women living with HIV give birth to healthy babies without passing on HIV.

Mildmay is the first specialist unit aiming to provide pioneering step-down care* for the homeless population of London and the surrounding regions

With homelessness in London and other major cities across the UK increasing, there is urgent need for highly focused, specialist care of the sort that Mildmay Hospital provides.

Registered Charity no: 292058

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