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HIV Information

HIV is the name of a virus. AIDS is the name for a collection of illnesses caused by this virus.


What is HIV?

HIV stands for Human Immunodeficiency Virus. ‘Immunodeficiency’ refers to the weakening of the immune system by the virus.


What is AIDS?

AIDS stands for Acquired Immune Deficiency Syndrome, and it is not the same as HIV. You cannot ‘catch AIDS’. AIDS is a collection of illnesses i.e., a syndrome, caused by a virus people acquire that weakens their immune system. Therefore, you have to have HIV to acquire the illnesses that weaken your immune system to the point you get an AIDS diagnosis.

During the 1980s to the mid-1990s most people who had a HIV diagnosis were eventually diagnosed with AIDS.

Now, in the 2020s only a very small number of people in the UK develop serious HIV related illnesses. Doctors in the UK don’t often use the term AIDS these days; they now talk about late-stage or advanced HIV.


How is HIV transmitted?

Contrary to what many people think, HIV is not an easy virus to catch or pass on.  HIV can only be passed on through certain body fluids, when a route into the body is available. Only certain body fluids, listed below contain HIV in high enough quantities to cause transmission. 


If someone with HIV has a detectable viral load (viral load is the amount of HIV in the blood – see below for information on an undetectable viral load) they can pass on HIV through the following body fluids:

  • blood

  • semen (including pre-cum, also known as pre-ejaculatory fluid)

  • vaginal fluid

  • anal mucus

  • breast milk


1. Blood

The risk of HIV transmission through blood comes when the person has a detectable viral load, and their blood enters another person’s body or comes into contact with a mucous membrane; these are parts of the body with wet, absorbent skin.


There’s also a risk if blood from a person who has a detectable viral load comes into contact with a cut or broken skin, giving HIV a way through the skin and into someone’s bloodstream. If blood gets onto skin that isn’t broken, there is no risk.


In a medical setting, it’s possible for HIV to be transmitted by someone accidentally cutting themselves with a blade or needle they have used to treat a person living with HIV. This is called a needlestick injury. The risk of being infected in this way is very low. However, if someone thinks they have been exposed to HIV through a needlestick injury, post-exposure prophylaxis (PEP) may be an option


2. Sexual transmission through semen, vaginal fluid, anal mucus


HIV can be transmitted through semen ((including pre-cum also known as pre-ejaculatory fluid), vaginal fluid and anal mucus, if you do not use a condom or if the condom slips off or tears when you are having sex. There is a small risk of catching HIV if you get infected semen or vaginal fluids in your mouth. There is absolutely no risk of catching HIV through kissing or mutual masturbation. If you are on treatment for HIV infection the anti-HIV drugs will normally reduce the amount of virus in your blood stream to such a low level that it is undetectable – this is called ‘an undetectable viral load’. If you have an undetectable viral load, you cannot transmit HIV through sexual contact.


3. Mother to baby transmission


A pregnant woman living with HIV can pass HIV on to her child through pregnancy, during childbirth or breast milk.  All pregnant women in the UK are offered an HIV test, and if you are HIV positive you can reduce the risk of passing on HIV to your baby through taking anti-viral drugs and avoiding breast feeding. In the UK it is very unusual for HIV to be passed from mother to baby. Less than 1% of babies born to women living with HIV in the UK are born with HIV themselves.


What do we mean by CD4 count? 

A CD4 count is mostly used to check the health of your immune system if you are infected with HIV (human immunodeficiency virus). Without treatment HIV attacks and destroys CD4 cells and your immune system will have trouble. Without treatment, HIV may destroy so many CD4 cells that your immune system will have trouble. In general, the higher your CD4 figure is, then the stronger your immune system is.


What is viral load? 

This measure shows how much HIV there is per cubic millilitre of blood. The lower this number, the less HIV is in the system and the less damage it can cause.  

The aim of putting people on treatment is to get the viral load count to undetectable levels.  This means that the amount of HIV in the system is at such low levels that ill-health is unlikely due to the HIV and the risk of passing on HIV is in effect close to zero.

Viral loads will vary between individuals, but the vast majority of people will quickly achieve an undetectable viral load once treatment has started.


What is an undetectable viral load?


HIV medication (antiretroviral treatment, or ART) works by reducing the amount of the virus in the blood to undetectable levels. This means the levels of HIV are so low that the virus cannot be passed on. This is called having an undetectable viral load or being undetectable.


It can take up to six months for some people to become undetectable from when they start treatment.


Evidence shows that for both gay couples and heterosexual couples that the risk of HIV transmission is effectively zero, which supports the campaign message U=U (Undetectable = Untransmittable).


HIV Statistics for the UK


There are around 107,000 people living with HIV in the UK.


In 2021, 2,955 people were newly diagnosed with HIV in the UK. For the UK, this is a 0.2% fall from 2,961 in 2020 and a 33% fall from 4,408 in 2019.



What is PEP (post exposure prophylaxis)?


PEP is a treatment that can stop an HIV infection after the virus has entered a person's body. It must be taken as soon as possible after exposure, preferably within 24 but definitely within 72 hours. PEP shouldn’t be viewed as a ‘morning after pill’ for HIV. It should be used as an emergency measure such as if a condom splits or comes off during sex. PEP will not protect you from other sexually transmitted infections or unplanned pregnancy.


PEP is free and the best place to get it is from a sexual health or HIV. If you need PEP and the clinics are closed, you can go to an Accident and Emergency department.



What is PrEP (Pre-exposure Prophylaxis)? 


PrEP is medication that can be taken by HIV-negative people before and after sex that reduces the risk of getting HIV. It’s available by free on the NHS.


HIV Testing


An HIV test is used to determine if someone is HIV positive and taking a HIV test has never been simpler. You can only know your HIV status by taking a HIV test and knowing your HIV status puts you in control of your health. A positive diagnosis means you can access the medical treatment and support you need to stay well.

Taking an HIV test is simple and quick and it’s easy to get one. You can get at test at various places in person, such as a sexual health clinic, some GP surgeries, some pharmacies, and some charities, or you can order a test online with free and paid for options. Most tests give you the result in a few minutes. 

  • HIV Clinic at Addenbrookes Hospital

Clinic 1a – HIV Clinic

Outpatient Department

Addenbrooke’s Hospital

Hills Road

Cambridge CB2 0QQ

01223 217766


General enquiries (not appointments):


Living with HIV and mental health

Emotional wellbeing and mental health are important for everyone, regardless of their HIV status. With access to HIV treatment, HIV has become a manageable long term medical condition. However, some people living with HIV will experience mental health problems. There are different reasons for this, including HIV-related stigma, self-stigma and treatment side effects. Sometimes mental health challenges are not directly linked to having HIV, but to other factors and life events.

If you are struggling with your mental health you should speak to a professional, e.g., your HIV clinician or GP and they should be able to refer you for support.

Dhiverse provides a free counselling service for people living with HIV click here.

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