HIV

HIV, the human immunodeficiency virus, attacks the white blood cells that defend the body against infection. Without treatment the immune system slowly weakens, until infections and some cancers that a healthy body would fight off begin to take hold. That advanced stage is called AIDS.

There is no cure, but there is very effective treatment. Medicines taken daily stop the virus multiplying, let the immune system recover and allow people to live long and healthy lives.

In the first weeks after infection some people get an illness like flu, with fever, headache, rash and a sore throat. Many people notice nothing at all.

After that, HIV usually causes no symptoms for years while it quietly damages the immune system. As the immune system weakens, the signs may include:

• Swollen glands in the neck, armpits or groin
• Weight loss without trying
• Fever or night sweats that keep coming back
• Diarrhoea that lasts for weeks
• A cough that will not clear
• White patches in the mouth, or infections that keep returning

See a doctor within a few days for a fever, night sweats, weight loss or a cough lasting more than two weeks, after a possible exposure at any earlier time, in pregnancy, or if HIV medicines have been stopped or have run out.

HIV passes from one person to another only through certain body fluids: blood, semen, vaginal fluids and breast milk. The usual routes are:

• Sex without a condom with a partner who has HIV
• Sharing needles, syringes or other injecting equipment
• From mother to child in pregnancy, at birth or through breastfeeding
• Unsafe injections, unscreened blood transfusions or unsterile medical procedures
• A needle-stick injury at work

It is not passed on by kissing, hugging, shaking hands, sharing food, water, utensils, towels or bedding, by toilet seats or swimming pools, or by insect bites.

• Sex without a condom when a partner's HIV status is not known
• Sharing needles or injecting equipment
• Injections, transfusions or procedures with equipment that has not been sterilised
• A needle-stick injury or blood splash at work
• Being born to a mother with untreated HIV, or being breastfed by her
• Not having been tested, so that an infection goes untreated

As the immune system weakens, infections that a healthy body keeps in check can become severe. Tuberculosis is the commonest of these. Others include a form of meningitis caused by a fungus, and severe bacterial infections.

Certain cancers, such as lymphoma and Kaposi sarcoma, also become more likely. Treatment started in good time prevents most of this, which is one of the reasons testing matters.

• Condoms, used correctly every time
• Knowing your own and your partner's status through testing, and screening for other sexually transmitted infections
• Preventive medicine taken before exposure, known as PrEP, for people at substantial risk
• Emergency preventive medicine after a possible exposure, known as PEP, started within 72 hours
• A new needle and syringe every time, and never sharing injecting equipment
• Testing in pregnancy, and treatment for the mother, which greatly reduces the chance of passing HIV to the baby
• Screened blood for transfusion, and sterile equipment for every procedure
• Treatment itself, because a person whose virus is undetectable does not pass it on sexually

HIV is diagnosed with a blood or oral fluid test. Rapid tests give a result the same day, and self-test kits let a person test in private, with a confirmatory test by a trained health worker before any diagnosis is made.

A test can be negative if it is done very soon after exposure, so a repeat test after the window your doctor advises may be needed. Once HIV is confirmed, the viral load and CD4 count show how much virus is present and how strong the immune system is. Babies born to mothers with HIV need a different kind of test, because antibody tests are not reliable under 18 months of age.

Treatment is with antiretroviral medicines, usually a combination taken once a day. They do not cure the infection, but they stop the virus multiplying, so the immune system can recover and stay strong.

Taken as prescribed, they bring the amount of virus in the blood down until it can no longer be detected. That protects the person's health and means HIV is not passed on to sexual partners. Doses are not skipped, because the virus starts multiplying again when the medicine stops.

Regular blood tests check the viral load, the CD4 count and how the body is handling the medicines. Any infection such as tuberculosis is treated alongside, and doctors also offer preventive treatment and vaccinations where they are needed.