HIV and AIDS Explained

HIV and AIDS are some of the most well-known illnesses around the world. Thanks to modern antiretroviral treatments and preventative options, HIV is now a highly manageable condition, and most people with HIV never develop AIDS.

The UK is striving to end HIV transmissions by 2030, and so understanding this virus has never been more important.

This guide has everything you need to know about HIV and AIDS, from causes and symptoms to diagnosis, treatment, and prevention methods like PrEP. So read on below to see what living well with HIV looks like today.

Three key takeaways

• Modern antiretroviral treatment means most people with HIV never develop AIDS, allowing them to live healthy lives when diagnosed early and treated properly.
• Practicing safer sex, and taking preventative medication, like PrEP can reduce your risk of ever getting HIV by nearly 100%.
• If you think that you are at risk of being HIV positive, you should contact your healthcare professional for a HIV test as soon as possible.

What is HIV?

HIV (human immunodeficiency virus) is a virus that increases your risk of serious illness by weakening your immune system.

It does this by targeting, attacking and destroying your CD4 T cells. These are crucial white blood cells that coordinate the immune system’s response to infections.

The most recent UK-wide estimate is that there are over 118,000 people living with HIV in the UK, with 5,200 of these being undiagnosed and not knowing they have HIV.

Even though there is currently no cure for HIV, early recognition, preventive treatments, and modern antiretroviral medications mean that most people never end up getting advanced HIV, or AIDS.

4 stages of HIV infection

Untreated HIV progresses through four stages, from the initial infection, to developing illness and ultimately late-stage HIV (AIDS).

1. Seroconversion illness

People with HIV experience a short illness soon after they contract it. This is known as the primary, or acute HIV infection.

For some, this can be so mild that it passes without being noticed. For others it may be more severe, requiring them to go and see a doctor.

In some instances, it is mistaken for the flu and overlooked. However, seroconversion is the period when someone with HIV is at their most infectious.

Common symptoms during seroconversion are:

• sore throat
• fever
• swollen glands
• muscle aches
• a rash over the body

2. Asymptomatic stage

After seroconversion, most people feel fine. The asymptomatic stage is when people with HIV don’t experience any symptoms and can last for several years.

While people in this stage may feel well, the virus is still active and is infecting new cells. It makes copies of itself and damages your immune system’s ability to fight illness. This is also referred to as stage 1.

3. Symptomatic stage

The longer people live without being treated for HIV, the higher the chance there is of developing infections. At this point, your immune system will not be able to fight these infections. Getting ill in one of these ways mean that you now have symptomatic HIV, or stage 2 HIV.

4. Late-stage HIV

Most people never experience late-stage HIV (AIDS, or stage 3 HIV), as it’s often diagnosed promptly and treatment prescribed straight away.

If HIV remains untreated and begins to cause a lot of damage to your immune system, this is where you may become ill from certain infections and cancers that are classed as AIDS-defining conditions.

What are the symptoms of HIV?

Symptoms of HIV vary from person to person, and can be often non-specific, meaning that they don’t belong to just one disease. These symptoms may include:

• weight loss
• night sweats
• thrush in the mouth
• an increase in herpes or cold sore outbreaks
• long-lasting diarrhoea

These symptoms normally appear when HIV has entered the second stage, although many people don’t experience any symptoms during this period.

HIV symptoms in women

Symptoms of HIV tend to be similar across all sexes. However, women with HIV are at an increased risk of:

• recurrent vaginal yeast infections
• other vaginal infections, like bacterial vaginosis
• changes to their menstrual cycle
• human papillomavirus (HPV)

Another important distinction between men and women with HIV is the additional risk that the virus can be transmitted to a foetus during pregnancy.

Thankfully, antiretroviral therapy is considered safe during pregnancy, and women receive this treatment are at a very low risk of transmitting HIV to their baby during pregnancy and delivery.

What are the causes of HIV?

HIV transmitted from person to person via differently bodily fluids, including:

• semen
• blood
• human milk
• pre-seminal fluid (pre-cum)
• vaginal or rectal fluids

It is important to note that not every bodily fluid from a person who has HIV can transmit HIV.

These fluids must come into contact with a damaged tissue or be directly injected into your bloodstream (from a syringe or needle) for HIV to be spread.

4 main ways HIV is spread

There are four main ways in which HIV is spread:

• Anal sex: Receptive anal sex (having a partner’s penis inside you) makes you much more likely to get HIV than insertive anal sex. HIV can enter the body through the lining of the rectum, as well as the opening at the tip of the penis, the foreskin, or cuts and sores on the penis.
• Vaginal sex: HIV can enter your body through the tissue that lines the vagina and cervix. Additionally, vaginal fluid and blood can once again enter through the tip of the penis, foreskin and any cuts or sores.
• Injection drug use: Used needles, syringes, and other injection equipment may have someone else’s blood in them, which can cause HIV to spread.
• Perinatal transmission: HIV can pass to a baby during pregnancy, childbirth, and when breastfeeding. This is the most common way that children can get HIV.

In either anal or vaginal sex, either partner can get HIV.

What is viral load?

Viral load is the amount of HIV in your blood. This is significant as evidence has been collected that shows the likelihood of passing on HIV is linked to the amount of virus in the blood.

Viral load is highest during the first stage of HIV and can remain high if you don’t get treated for HIV.

How is HIV diagnosed?

It's easier than ever to get a test for HIV, in part because there are now multiple types of tests available. Different tests are better for different people, and which test is best for you will be determined by your healthcare professional.

Antibody/antigen (4^th generation) tests

This is the most commonly used method of testing for HIV. This test involves drawing blood from a vein and testing it for antibodies (the type of protein that responds an infection) and antigens (the part of the virus that sets the immune system off). There is also a rapid test that is done with blood from a finger stick.

Antibody tests

An antibody test only looks for the antibodies but can do so in either your blood or saliva. These tests are done using blood tests or mouth swabs and can produce results within 20-30 minutes.

This is the only HIV self-test that is available and can be bought over the counter. If you test positive, you should follow up with your healthcare professional to confirm your results.

Nucleic acid test (NAT)

This test is not used for general screening due to its increased cost but is instead used for people who have early symptoms of HIV. This test doesn’t look for antibodies, instead, looking for the virus itself. Additionally, a NAT can detect HIV sooner than the other types of tests, typically between 10 and 33 days after exposure.

How do you treat HIV?

If you’ve received a diagnosis for HIV, you should begin your treatment as soon as possible, regardless of what your viral load is.

Antiretroviral drugs

Many antiretroviral therapy medications are approved to treat HIV. They work by preventing the virus from reproducing - reducing the amount of virus in the body. Because the viral load falls, far fewer CD4 cells are attacked and destroyed.

The various types of antiretroviral therapy medicines are grouped into different categories:

• nucleoside reverse transcriptase inhibitors (NRTIs)
• non-nucleoside reverse transcriptase inhibitors (NNRTIs)
• integrase inhibitors (INIs or INSTIs)
• entry inhibitors (CCR5 antagonists)
• protease inhibitors
• long-acting injectable treatment

Generally, when starting treatment, you’ll be prescribed three HIV medications from at least two of these categories. This is to try and prevent HIV from forming a resistance to any of the medications.

These medications must be taken every day, exactly as prescribed. If they’re not taken properly, resistance can develop.

Ways to prevent HIV

As the UK strives to be the first country in the world to end HIV transmissions by 2030, there are more options than ever before to help prevent people from getting HIV.

Post-Exposure Prophylaxis (PEP)

PEP is an anti-HIV medication that’s prescribed if you’ve had potential exposure to HIV. Evidence suggests that PEP reduces the chances of HIV infection by approximately 80%.

It should be started within 72 hours of the exposure and usually won’t be prescribed after 72 hours.

Before you’re prescribed PEP, you’ll need to have a HIV test, as if HIV is detected, further tests need to be done. A secondary HIV test is required after given PEP to confirm if the medication has been effective.

Pre-Exposure Prophylaxis (PrEP)

PrEP is a course of medication taken if you don’t have HIV, in order to lower your chance of acquiring HIV.

There are different ways you can take PrEP. Some people take it every day for continuous protection; others take a more ‘event based’ approach, only taking PrEP when they expect to have sex. If you take it properly, it provides a near 100% protection against HIV. 

PrEP is very effective and is widely available, both on the NHS and privately following a consultation.

Cabotegravir

Last year, the NHS announced they were rolling out a new, long-acting injection to prevent HIV called cabotegravir, sold under the brand name Apretude. This is currently only for people who cannot have PrEP tablets, for reasons like interactions with other medication, or difficulty swallowing tablets.

It is given as an injection that is administered once a month for the first two months, and then once every two months for however long you stay on the drug. These injections have to be administered by a healthcare professional.  

Barrier protection

Practicing safer sex and using barrier protection is one of the best ways you can prevent the transmission of HIV. The most common way that HIV is transmitted is through anal or vaginal sex in which a condom or other barrier method is not used.

While this doesn’t completely eliminate any risk of getting HIV, taking precautions such as getting HIV tests and using condoms are still effective ways to help keep you safe.

If you’re not sure on how to use one, then we’re here to help with our guide to how to put on a condom.

What is AIDS?

AIDS (acquired immune deficiency syndrome), now often referred to as stage 3, late-stage or advanced HIV, is diagnosed when HIV has severely damaged the immune system or when someone develops one or more AIDS‑defining illnesses.

 Examples of these are:

• tuberculosis (TB)
• cancer
• pneumonia

While modern antiretroviral treatments (ART) have made HIV manageable, and most people don’t develop late-stage HIV. However, if you do, life expectancy is often only a few years.

Causes of AIDS

AIDS is caused by HIV – if someone has not contracted HIV, they cannot get AIDS.

The levels of the CD4 white blood cell levels in a healthy person is 500-1500 per mm³. As HIV destroys these cells, if someone’s levels of CD4 drops below 200, they have AIDS.

Additionally, if someone with HIV develops an infection associated with HIV, like the ones listed above, they can receive a diagnosis of AIDS even if their CD4 count is above 200.

Living with HIV

Staying healthy is key to living well with HIV, as modern HIV treatment now takes care of most associated risks.

There are a number of trusts, charities and clinics that can provide support and offer advice on how to navigate legal issues, parenthood and relationships. A notable example in the UK is the Terrence Higgins Trust.

They also help with offering support for mental health, as depression is twice as common among people living with HIV.

Frequently asked questions about HIV and AIDS

What is the main difference between HIV and AIDS?

The main difference between HIV and AIDS is that HIV is a manageable viral infection with effective treatment, whereas AIDS is the advanced stage of HIV that develops when the immune system becomes severely damaged.

Without treatment, AIDS can be life‑threatening within a few years, but with modern HIV care, people can live for many years and may even return to a healthier immune state.

How long can you live with HIV without knowing?

The asymptomatic stage of HIV (in which you do not experience any symptoms) can last for a few months before you become symptomatic.

If you are concerned whether you may have HIV, you should contact your GP for a blood test.

Is there a vaccine for HIV?

While there is currently no cure for HIV, there is effective preventative treatment, in addition to modern antiretroviral medicines that allow it to be managed, while also reducing likelihood of transmission.

Is a rash a symptom of HIV?

Many people with HIV experience a rash as one of the first symptoms. An HIV rash often appears as multiple small lesions that are flat and raised.

Can you get HIV from kissing?

No. You cannot get HIV from kissing, as HIV is not transmitted through saliva.

Sources

• HIV Statistics. Terrence Higgins Trust. [accessed on 14/01/2026]
• Stages of HIV infection. (2025). Terrence Higgins Trust. [accessed on 14/01/2026]
• HIV and AIDS. (2025). NHS. [accessed on 19/01/2026]
• How HIV Spreads. (2024). CDC. [accessed on 19/01/2026]
• Getting Tested for HIV. (2025). CDC. [accessed on 20/01/2026]
• PEP and PrEP. Sexual Health London. [accessed on 20/01/2026]