HIV and AIDS - Causes

 In the UK, most cases of HIV are caused by having sex without a condom with a person who has HIV.

A person with HIV can pass the virus to others whether or not they have any symptoms. People with HIV are more infectious in the weeks following infection.

HIV treatment significantly reduces the risk of someone with HIV passing it on.

Sexual contact

According to Public Health England, 95% of people diagnosed with HIV in the UK in 2011 acquired HIV through sexual contact.

The main routes of transmission are unprotected vaginal and anal sex. It is also possible to catch HIV through unprotected oral sex, but the risk is much lower.

The risk of HIV transmission through oral sex will be higher if the person giving oral sex has mouth ulcers, sores or bleeding gums and/or if the person receiving oral sex has been recently infected with HIV (and has a lot of the virus in their body) or another sexually transmitted infection.

The type of sex also makes a difference to the level of risk:

    performing oral sex on a man with HIV carries some risk, particularly if he ejaculates (comes) in your mouth
    it is possible to catch HIV by performing oral sex on a woman with HIV, particularly if she is having a period, although this is considered to be extremely low risk
    receiving oral sex from someone who has HIV is also extremely low risk as HIV is not transmitted through saliva

Other risk behaviors

Other ways of getting HIV include:

    sharing needles, syringes and other injecting equipment
    from mother to baby before or during birth or by breastfeeding
    sharing sex toys with someone infected with HIV
    healthcare workers accidentally pricking themselves with an infected needle (this risk is extremely low)
    blood transfusion (now very rare in the UK, but still a problem in developing countries)

How is HIV transmitted

HIV is not passed on easily from one person to another. The virus does not spread through the air like cold and flu viruses.

HIV lives in the blood and in some body fluids. To get HIV, one of these fluids from someone with HIV has to get into your blood.

The body fluids that contain enough HIV to infect someone are:

    semen
    vaginal fluids, including menstrual blood
    breast milk
    blood
    lining inside the anus

Other body fluids, like saliva, sweat or urine, do not contain enough of the virus to infect another person.

The main ways the virus enters the bloodstream are:

    by injecting into the bloodstream (with a contaminated needle or injecting equipment)
    through the thin lining on or inside the anus and genitals
    through the thin lining of the mouth and eyes
    via cuts and sores in the skin

HIV is not passed on through:

    kissing
    spitting
    being bitten
    contact with unbroken, healthy skin
    being sneezed on
    sharing baths, towels or cutlery
    using the same toilets or swimming pools
    mouth-to-mouth resuscitation
    contact with animals or insects such as mosquitoes

How HIV infects the body

HIV infects cells of the immune system, the body’s defence system, causing progressive damage and eventually making it unable to fight off infections.

The virus enters cells in the immune system called CD4 cells + ve lymphocyte cells, which protect the body against various bacteria, viruses and other germs.

It uses the CD4 cells to make thousands of copies of itself. These copies then leave the CD4 cells, killing them in the process.

This process continues until eventually the number of CD4 cells, also called your CD4 count, drops so low that your immune system stops working.

This can take about 10 years, during which time you will feel and appear well.

Who is most at risk?

People who are at higher risk of becoming infected with HIV include:

    men who have had unprotected sex with men
    women who have had sex without a condom with men who have sex with men
    people who have had sex without a condom with a person who has lived or travelled in Africa
    people who inject drugs
    people who have had sex without a condom with somebody who has injected drugs
    people who have caught another sexually transmitted infection
    people who have received a blood transfusion while in Africa, eastern Europe, the countries of the former Soviet Union, Asia or central and southern America
 

tags: HIV and AIDS - Causes, Causes, HIV and AIDS, AIDS, HIV, Who is most at risk?, Sexual contact, Other risk behaviors, How is HIV, transmittedHow HIV infects the body, In the UK, most cases of HIV are caused by having sex without a condom with a person who has HIV.