How is HIV Transmitted?

How can a person catch HIV?

HIV is usually transmitted in the following ways:

An infectious body fluid (such as blood, semen and vaginal or anal secretions*) gets inside another person. This allows the virus to enter their blood stream. This can happen during vaginal and anal sex (and sometimes oral sex too though this is much less common) – or when an object (eg, a sex toy) that has a body fluid on it goes from inside one person and into another.

HIV can also be passed on if drug users share injecting equipment (needles, syringes, swabs, spoons and other items) that has been used by someone with HIV.

Unless she takes HIV medication, if a woman has HIV she can give birth to a baby who also becomes infected. This often happens during child birth but can also take place while breastfeeding or in the womb before the baby is born.

In countries that don’t have strict checks on the safety of their blood supply (this began in the UK in 1985), receiving contaminated blood can pass the virus on. This could also happen in countries that don’t screen other blood products, organs or sperm.

* these are fluids or kind of sticky lubrication that cover the inside of the vagina or anus

Although HIV could be passed on any time unprotected sex with an infected person happens, it doesn’t get passed on every time. These make it more likely to be transmitted:

  • High viral load (the amount of HIV in someone’s blood and other body fluids) – it’s very high in the first weeks or months after someone is infected. Taking HIV drugs will lower viral load a lot.
  • If either partner has a sexually transmitted infection (they make it easier for HIV to leave one body and enter another).
  • The type of exposure to the virus: anal sex is higher risk than vaginal sex, both are higher risk than oral sex. Sharing drug injecting equipment is higher risk than all of them.
Page content supplied by Copyright 2012 © Terrence Higgins Trust.

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