Vaginal sex (Intercourse)
HIV is found in the sexual fluids of an infected person. For a man, this means in the fluids which come out of the penis before and during sex. For a woman, it means HIV is in the fluids produced by the vagina before and during sex to help make intercourse easier.
If a man with HIV has vaginal intercourse without a condom, infected fluid can pass into the woman's blood stream through a tiny cut or sore inside her body. Such a cut or sore wouldn't always be visible, and could be so small that the woman wouldn't know about it.
If a woman with HIV has sexual intercourse without a condom, HIV could get into the man's blood through a sore patch on his penis or by getting into the tube that runs down the penis.
If there is any contact with blood during sex, this increases the risk of infection. For example, there may be blood in the vagina if intercourse occurs during a woman's period.

Oral sex
Oral sex with an infected partner does carry some risk of infection. If a person sucks on the penis of an infected man, for example, infected fluid could get into the mouth. The virus could then get into the blood if you have bleeding gums or tiny sores or ulcers somewhere in the mouth.
The same is true if infected sexual fluids from a woman get into the mouth of her partner.
But infection from oral sex alone seems to be very rare. Click Here for more information about Oral Sex.

Anal sex
If a couple have anal intercourse the risk of infection is greater than with vaginal intercourse. The lining of the anus is more delicate than the lining of the vagina, so it's more likely to be damaged during intercourse, and any contact with blood during sex increases the risk of infection.

Injecting drugs
There is a good likelihood of becoming infected with HIV if you share injecting equipment with someone who has the virus. The virus can be passed by sharing needles, syringes, spoons, filters and water. Disinfecting equipment between use can reduce the chance of transmission, but doesn't eliminate it.

Blood transfusions
Some people have been infected through a transfusion of infected blood. These days, in most countries all the blood used for transfusions is now tested for HIV. In those countries where the blood has been tested, HIV infection through blood transfusions is now extremely rare.

Blood products
Blood products, such as those used by people with Hemophilia, are now heat-treated to make them safe.

Mother to child transmission
An infected pregnant woman can pass the virus on to her unborn baby either before or during birth. HIV can also be passed on during breastfeeding.
If a woman knows that she is infected with HIV, there are drugs that she can take to greatly reduce the chances of her child becoming infected.

Infection in the health-care setting
Some health-care workers have become infected with HIV by being stuck with needles containing HIV-infected blood. A very few have become infected by HIV-infected blood getting into the health-care worker's bloodstream through an open cut or splashes into a mucous membrane (e.g. eyes or the inside of the nose).
There have only been a few documented instances of patients becoming infected by a health-care worker.

Tattoos / piercings
Anything which allows another person's body fluids to get inside your body is risky. If the equipment is not sterile, having a tattoo done could carry a very small risk. In the UK, there are hygiene regulations governing people who do tattoos and piercings, and all instruments used should be sterile. If you are thinking of having a tattoo or piercing, ask staff at the shop what procedures they take to avoid infection.

Kissing
At the moment, scientific opinion is pretty clear that you cannot become infected with HIV through kissing.
To become infected with HIV you must get a sufficient quantity of HIV into the bloodstream. Saliva does contain HIV, but the virus is only present in very small quantities and as such, cannot cause HIV infection.
Unless both partners have large open sores in their mouths, or severely bleeding gums, there is no transmission risk from mouth-to-mouth kissing.

Sneezing, coughing, sharing glasses/cups, etc
HIV is unable to reproduce outside its living host, except under very extreme laboratory conditions. HIV does not survive well in the open air, and this makes the possibility of this type of environmental transmission remote. In practice no environmental transmission has been seen.
This means that HIV cannot be transmitted through spitting, sneezing, sharing glasses or musical instruments.
You also can't be infected in swimming pools, showers or by sharing washing machines or toilet seats.

Insects
Studies conducted by many researchers have shown no evidence of HIV transmission through insects, even in areas where there are many cases of AIDS and large populations of insects such as mosquitoes. Lack of such outbreaks, despite considerable efforts to detect them, supports the conclusion that HIV is not transmitted by insects.
Also, HIV only lives for a short time and does not reproduce in an insect. So, even if the virus enters a mosquito or another sucking or biting insect, the insect does not become infected and therefore cannot transmit HIV to the next human it feeds on or bites.

Injecting with sterile needles
Drug use with sterile works will not transmit HIV either, as long as clean works are used every time - this means needle, syringe and spoon, water and filters. There are still many other risks associated with injecting drug use. And, if you are on drugs, even alcohol, this may cloud your judgment and make you more likely to become involved in risky sexual behavior - it's harder to make the effort to use a condom when you're off your head.

Protected sex
Condoms, if used correctly and consistently, are highly effective at preventing HIV transmission. There are myths saying that 'some very small viruses can pass through latex' - this is not true.
Anal sex is not necessarily a risk if unbroken condoms are used and there is no blood-to-blood contact. You can't 'create' HIV by having anal sex.

There are three main types of HIV test.

The first type of test is the HIV antibody test. This test shows whether a person has been infected with HIV, the virus that causes AIDS. Information on this page concentrates principally on HIV antibody testing. Antibody tests are also known as ELISA (Enzyme-Linked Immunosorbent Assay) tests.

The second type of test is an antigen test. Antigens are the substances found on a foreign body or germ that trigger the production of antibodies in the body. The antigen on HIV that most commonly provokes an antibody response is the protein P24. Early in the infection, P24 is produced in excess and can be detected in the blood serum by a commercial test (although as HIV becomes fully established in the body it will fade to undetectable levels). P24 antigen tests are sometimes used to screen donated blood, but they can also be used for testing for HIV in individuals, as they can detect HIV earlier than standard antibody tests. Some of the most modern HIV tests combine P24 and other antigen tests with standard antibody identification methods to enable earlier and more accurate HIV detection.

The third type of test is a DNA or RNA test. These types of tests detect the genetic material of HIV itself, and can identify HIV in the blood within a week of infection. DNA/RNA tests come in a number of forms. Babies born to HIV positive mothers may be tested using a type of DNA test called a PCR (Polymerase Chain Reaction). Blood supplies in developed countries are screened for HIV using an RNA test known as NAT (Nucleic Acid-amplification Testing). When a person already knows that she or he is infected with HIV, they may also have a viral load test to detect HIV genetic material and estimate the level of virus in the blood. DNA/RNA tests are rarely used to test for HIV in adults, as they are very expensive and more complicated to administer than a standard antibody or P24 test.