What is HIV and How Does it Affect the Body?

Dr Ravi Gowda
6 days ago
8 min read

Updated: 4 days ago

When HIV was first identified in the early 1980s, a diagnosis was almost always a death sentence. I started my career in infectious diseases at a time when the consequences of undiagnosed or untreated HIV were still very much visible on our wards and I've seen, first hand, just how far we've come. People living with HIV today, if diagnosed early and treated properly, can expect to live a near-normal lifespan. But despite how far we've come, HIV remains a significant global health problem and there are still far too many misconceptions about it. Knowing your status is where it all starts.

In this article, we will cover:

What is HIV?
How does HIV affect the human body?
What are the symptoms of HIV — in men and women?
How long does it take for HIV symptoms to show?
How do you get HIV?
How is HIV tested?
HIV treatment
How to prevent HIV
Frequently asked questions about HIV

What is HIV?

HIV stands for Human Immunodeficiency Virus. It's a virus that attacks the immune system specifically, white blood cells called CD4 T-lymphocytes (or T-cells) which your body relies on to fight off infections and disease.

Without treatment, HIV gradually weakens the immune system to the point where the body can no longer defend itself against everyday infections and certain cancers. This advanced stage is known as Acquired Immune Deficiency Syndrome, or AIDS. So, HIV is the virus; AIDS is an advanced form of the disease that develops when HIV is left untreated.

According to UNAIDS, around 39.9 million people are living with HIV worldwide. In the UK, the UK Health Security Agency (UKHSA) estimates there are approximately 105,200 people living with HIV. The good news is that 97% of those diagnosed are on effective treatment.

How Does HIV Affect the Human Body?

HIV attacks and destroys CD4 T-cells the very cells your immune system relies on to coordinate its defences. As the CD4 count falls, the body becomes increasingly vulnerable to what we call opportunistic infections illnesses that a healthy immune system would normally keep well in check, such as pneumocystis pneumonia, toxoplasmosis and certain cancers including Kaposi's sarcoma and lymphoma.

What are the Symptoms of HIV?

The trouble with HIV is that many people have no symptoms at all, particularly in the early and chronic stages. People can pass it on without ever knowing they have it - which is one of the main reasons it continues to spread. If symptoms do occur, they most commonly appear during what we call seroconversion which is the body's initial response to the virus.

Sadly, I’ve seen many HIV patients present with tuberculosis, and other infections such as pneumocystis pneumonia. We’ve also diagnosed new HIV infections in patients who had presented with oral thrush or severe shingles – simply because we were alert to the fact that they might have a weakened immune system.

HIV Symptoms in Men

In men, the first signs of HIV infection, known as the acute retroviral syndrome or seroconversion illness, typically appear 2 to 4 weeks after initial infection. These can include:

Fever
Persistent fatigue (see our article on causes of fatigue)
Sore throat
Swollen lymph nodes — the glands in your neck, armpits or groin
Muscle and joint pain
HIV rash — typically a flat or slightly raised red rash on the trunk, face or limbs
Headache
Nausea and diarrhoea
Mouth ulcers

These symptoms are non-specific and can easily be mistaken for flu or another viral illness. If you have had a potential HIV exposure recently and develop any of these symptoms, get tested.

HIV Symptoms in Women

Women get many of the same early HIV symptoms as men. In addition, women may also notice:

Recurrent or more severe vaginal infections, such as persistent thrush
Changes to their menstrual cycle
More vulnerable to infections of the neck of the womb such as HPV (Human Papilloma Virus) or cervical cancer

Just like men, you can have HIV and feel perfectly well. This is why regular STI testing — including HIV testing - matters so much, especially if you have new or multiple sexual partners.

HIV Rash - what to look out for: The HIV rash is one of the more recognisable early signs of HIV infection. It typically appears within 2 to 3 weeks of exposure during seroconversion, usually presenting as a red, flat or maculopapular rash on the chest, back or face and in most cases it's not itchy. If you develop an unexplained rash alongside flu-like symptoms, please seek medical advice and get tested.

How Long Does it Take for HIV Symptoms to Show?

The seroconversion illness typically occurs 2 to 4 weeks after infection - but many people either experience very mild symptoms or none at all.

After seroconversion, HIV can remain completely silent for many years - in some cases a decade or more during which time you may feel perfectly well, yet the virus is still active and can still be transmitted. This is exactly why testing matters. You simply won't know you have it unless you get tested.

You can read more about the importance of HIV testing and World AIDS Vaccine Day in our dedicated article.

How Do You Get HIV?

HIV is found in specific bodily fluids such as blood, semen (including pre-seminal fluid), rectal fluids, vaginal fluids and breast milk, from someone who is HIV positive and has a detectable viral load.

Here’s how you can and cannot become infected with HIV:

HIV is one of several STIs that have been rising in the UK in recent years. You may also find our articles on gonorrhoea and chlamydia useful reading.

Can You Get HIV from Kissing?

No. HIV cannot be passed on through kissing. The concentration of HIV in saliva is far too low to cause infection. See above.

How HIV is Tested

HIV testing has come a long way. The most reliable blood tests used in the UK are 4th generation HIV tests, which detect both HIV antibodies and the p24 antigen — a protein produced by the virus itself. Testing for both means we can pick up infection much earlier than older tests could manage.

The window period — the time between exposure and when a test can reliably detect infection is:

45 days for a 4th generation test (detecting over 99% of infections by this point)
90 days for a fully definitive result

If you have had a potential HIV exposure, don't wait for symptoms before getting tested. At Health Klinix, we offer a confidential STI test including HIV, with results usually back within 1 to 3 working days. NHS HIV testing services are also available through your local sexual health clinic.

HIV Treatment

Modern HIV treatment, known as antiretroviral therapy (ART) has transformed what it means to live with HIV. Most people in the UK now take a single tablet once a day, containing a combination of antiretroviral drugs, with side effects that are generally well tolerated.

The goal of ART is to suppress the viral load to undetectable levels. When this is achieved, the immune system recovers, the person stays well, and crucially, they cannot transmit HIV sexually. This is known as the Undetectable = Untransmittable (U=U) principle, backed by landmark research including the PARTNER2 study (Lancet, 2019). Regular monitoring of CD4 count and viral load also allows us to confirm treatment is working.

We’ve has severely unwell patients with serious infections such as cryptococcal meningitis make a complete recovery with prompt anti-fungal treatment and ART. They now lead completely normal lives.

How to Prevent HIV

There's a lot you can do to protect yourself and your partner(s). Here's what we'd recommend:

Use condoms - consistently and correctly for vaginal and anal sex
PrEP (Pre-Exposure Prophylaxis) - medication taken by HIV-negative people before sex to prevent infection. PrEP is now available free through the NHS and works very well when taken correctly
PEP (Post-Exposure Prophylaxis) - emergency medication that can prevent HIV if taken within 72 hours of a potential exposure. The sooner it's started, the better — so don't delay
Get tested regularly - know your status and encourage your partner(s) to do the same
Don't share needles - or drug-injecting equipment

If you're HIV positive and on effective ART with an undetectable viral load, you cannot pass HIV on sexually (U=U)

Frequently Asked Questions About HIV

Is there a cure for HIV?

There's no widely available cure for HIV at the moment. However, antiretroviral therapy is so effective that many people living with HIV have undetectable viral loads, functioning immune systems and lead completely normal lives. Research into a cure is ongoing and there is real, cautious optimism in the scientific community.

How long can a person living with HIV patient live?

Get diagnosed early and take your treatment consistently, and there's no reason you can't expect a near-normal lifespan. Research has shown that a 21-year-old starting treatment promptly can expect to live well into their 70s. Early diagnosis and sticking to treatment that's what makes the difference.

How does HIV affect everyday life?

Many people living with HIV work, have relationships, have children and travel in short, they lead full and normal lives. The day-to-day reality is taking your medication, attending regular check-ups, and having your CD4 count and viral load monitored. Stigma is still, sadly, very real but attitudes are shifting, so we’re hopeful.

What not to do if you're HIV positive

If you're HIV positive, there are some things you shouldn't do:

Don't delay starting treatment - the sooner you start, the better for your health and for others
Don't stop your medication without medical advice — the virus will rebound
Don't have unprotected sex before you have an undetectable viral load
Don't share needles or drug-injecting equipment
Don't ignore new or unusual symptoms — with a weakened immune system, you may develop rare infections

How does HIV become AIDS?

AIDS develops when HIV has severely damaged the immune system. This means a CD4 count below 200 cells per cubic millimetre, or the development of a specific AIDS-defining illness such as pneumocystis pneumonia, Toxoplasma encephalitis or certain lymphomas. With modern treatment, very few people in the UK progress to AIDS now.

How quickly can HIV be transmitted?

HIV can be transmitted at any point during unprotected sexual contact or needle sharing with someone who has a detectable viral load. The risk is highest during the acute seroconversion phase, when viral load peaks. If someone is on effective ART with an undetectable viral load, they cannot pass HIV on sexually.

How soon can HIV be detected in a blood test?

With a 4th generation HIV test, most infections can be reliably picked up from around 45 days after exposure. Testing before this window period can give a false negative result. If you've had a potential exposure in the last 72 hours, seek PEP immediately — don't wait to test. Time really does matter here.

HIV has gone from being one of the most feared diagnoses in medicine to a manageable long-term condition. With the right treatment, started early, people living with HIV can lead long, healthy and fulfilling lives. But none of that is possible without knowing your status.

If you're worried, or if you've had unprotected sex with a new partner, go and get tested. At Health Klinix, we offer a confidential STI test including HIV, with results usually back within 1 to 3 working days. Testing saves lives, it really is that simple.

Book an STI Test

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