About HIV

Human immunodeficiency virus (HIV) is a sexually transmitted infection and a blood borne virus.

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What is it?

Human immunodeficiency virus (HIV) is a sexually transmitted infection and a blood borne virus. There are approximately 100,000 people living with HIV in the UK. HIV infection results in the progressive failure of the human immune system, a part of the body that fights infections and prevents cancers. This means without treatment an infected person will eventually develop a range of progressively more serious and ultimately life-threatening infections and cancers.

How is it spread?

HIV is usually passed on (transmitted) from an HIV positive person through the following routes:

  • Condomless penetrative vaginal or anal sex. Less commonly: oral sex or sharing sex toys that have body fluids on, such as semen or anal or vaginal secretions.
  • Injecting drugs and sharing injecting equipment (needles, syringes, spoons)
  • Receiving blood (transfusion) or blood products from an HIV positive person.
  • Transmission from a HIV positive mother to her child during pregnancy, labor, or when nursing.

HIV positive individuals are significantly more likely to transmit the virus in the first few months after acquiring the infection, when they have very high levels of the virus (viral load) in their body fluids. HIV positive individuals become significantly less likely to transmit after they start taking HIV treatment, and their viral load becomes undetectable or fully suppressed - this usually takes up to six months. After six months with an undetectable viral load the chances of passing HIV on to someone else is zero.


HIV positive individuals often display no or minimal symptoms for the first few years. In those who do have symptoms, they can be variable and overlap with many other common conditions. This can partly explain why the diagnosis of HIV can be missed or delayed as symptoms are put down to other reasons.

Within six weeks transmission, approximately 50% of people will suffer a short flu like illness (lasting around two weeks) called a seroconversion illness, with features such as a general body rash, sore throat, fever, tiredness, diarrhea, joint and muscle pains and swollen lymph glands in the armpits, neck, or groin.

After this time many people do not experience any symptoms, sometimes for many years, but they can still pass on (transmit) the virus and their immune system will continue to be attacked and damaged by the virus.

How does it affect you?

Without treatment, an HIV positive person will eventually show signs of immune system impairment and develop a range of HIV symptoms such as thrush in their mouth, cold sores/ulcers on their mouth or genitals, general tiredness, night sweats, weight loss, warts on their skin, mouth or genitals, shingles, recurrent gut infections. Later they may face more serious and life-threatening conditions such as PCP pneumonia, tuberculosis, brain infections, and cancers like lymphoma. This collection of more serious illnesses and conditions is called AIDS (Acquired Immunodeficiency Syndrome).

Diagnosis (and testing)

A simple blood test can detect HIV infection. The test is highly accurate if performed 45 days after your last risk or exposure. This means, depending on the level of recent risk, and if your initial test was negative for HIV, it may be advisable to repeat the HIV test again after this “window period.”

When should I take a test?

The Centers for Disease Control (CDC) recommend that everyone between the ages of 13 and 64 should get tested for HIV at least once in their lifetime, and more often for those at higher risk.

We recommend you consider getting tested for HIV:

  • If you recently had unprotected sex with a new partner.
  • If you are pregnant, or are planning on getting pregnant.
  • When starting PEP, particularly in cases of sexual assault and occupational needle prick injuries.
  • Upon completing PEP.
  • Quarterly, whilst taking PrEP.
  • If you have unprotected sex with multiple sexual partners, or if you have a sexual partner with someone else who has unprotected sex with multiple partners.
  • If a sexual partner is HIV positive.
  • If you inject drugs intravenously or use shared needles.
  • If you exchange money or goods for sex or drugs.
  • If you already have tuberculosis or hepatitis.
  • If a baby is born to a woman who is HIV-positive.


These days treatment for HIV (antiretroviral therapy) is highly effective. Antiretroviral therapy is not a cure, but people diagnosed with HIV who start treatment as soon as possible can expect to live long and healthy lives. The treatment is usually simple to take, has few side effects and is very robust in controlling/suppressing HIV, but it does mean taking it for life.

If your test result shows suspected HIV infection, you will be referred by the health adviser team to a sexual health clinic of your choice to receive further (confirmatory) HIV blood tests. The clinic will discuss the infection in more detail and if your result confirms HIV infection, they will refer you to an outpatient HIV clinic for treatment.

The following tests are commonly performed in the HIV outpatient setting.  The CD4 blood test refers to your CD4 cell (or T cell) count and is a rough measure of your immune system. The CD4 helper T-lymphocyte is the predominant immune cell that the HIV virus infects and destroys. Over time the body can’t effectively replace these lost CD4 cells, and the size and function of this cell population declines and as it does so, the ability of your immune system to fight infection will also deteriorate. The lower the CD4 count the less able your immune system is to fight infection and the more serious and extensive the range of infections you become susceptible to.

The HIV viral load is a measure of how much replicating HIV is found in the circulating blood. In an HIV positive person this usually varies from a few hundred to several million copies/ml. In patients on HIV treatment, the viral load is an accurate measure of how effective treatment is and the treatment aim is for the viral load to reach an "undetectable" level. Treatment not only prevents you developing AIDS but significantly reduces the transmission risk of passing the virus on to your partner(s).

Contacting partners

If you are diagnosed with HIV you need to inform all your sexual partners dating back to the time of your last HIV negative test (and sometimes informing all partners in your life if you have never tested for HIV before).

If you are HIV positive and have had condomless sex with a partner in the last 3 days, they may be eligible for post exposure prophylaxis (PEP). Please see the relevant section (PEP) about this.


To prevent HIV transmission use condoms for penetrative sex, do not share injecting equipment and have regular STI check-ups. Encourage your partner to have regular STI check-ups also. You should also avoid donation of semen, organs, or blood if you are HIV positive.

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