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Blood cells

If someone has HIV and a detectable viral load, then the virus can be found in their blood and passed on.

People with HIV who are on effective treatment and have an undetectable viral load cannot pass on HIV through any of their body fluids.

How do you get HIV from contact with blood?

The risk of HIV transmission through infected blood comes when it enters another person’s body or when it comes into contact with a mucous membrane. These are parts of the body with wet, absorbent skin such as:

  • eyes
  • vagina
  • head of the penis
  • inside of the anus
  • mouth.

There’s also a risk if blood from a person who has a detectable viral load comes into contact with a cut or broken skin, giving HIV a way through the skin and into someone’s bloodstream. If blood gets onto skin that isn’t broken, there is no risk.

If a woman has HIV her menstrual blood also carries a risk of transmission if she has a detectable viral load.

When someone with HIV is on effective treatment and has an undetectable viral load, they cannot pass on HIV. It can take up to six months on treatment to become undetectable.

When is a person with HIV infectious?

Someone with HIV is infectious if they have a detectable viral load.

The risk is highest during the first few months after infection when they have very high levels of the virus in their body fluids and may not yet have been diagnosed and therefore won’t be on treatment.

Early diagnosis means a person can start treatment to reduce their viral load to undetectable levels and protect their health.

Find out more about this with our guide to what happens inside the body after HIV infection.

How to be safe when coming into contact with blood

Friction during sex can cause some bleeding, possibly too small to notice or in a part of the body where it can’t be seen. A condom will act as a barrier against any contact with blood during sex.

As well as sex, sharing drug injecting equipment is another way infected blood can get into someone’s body. This can be avoided by using fresh needles and not sharing needles, syringes and other equipment. The same goes for people who inject steroids.

If you’re HIV negative and taking Pre-exposure prophylaxis (PrEP) you’ll be protected to a large extent against getting HIV if you come into contact with infectious blood.

Again, if the person is on effective treatment and their viral load is undetectable they won’t be able to pass on HIV, however there are other serious viruses such as hepatitis B and hepatitis C which can be also passed on through blood.

What should I do if I need to clean up blood?

Where someone has a detectable viral load HIV does not usually survive long outside of the body, but contact with blood (especially on broken skin) should be avoided. (Blood infected with hepatitis C can survive in dried blood at room temperature for several weeks, and blood infected with hepatitis B can survive for around a week outside the body.)

To clean up blood that has been spilled on surfaces wear rubber gloves, mop up the liquid using bleach and warm water (one part bleach to 10 parts water). Use warm, soapy water to clean away blood spilled on someone’s body.

Put the waste, used gloves and bloodied clothes in a plastic bag, seal and throw away.

Can you get HIV from blood transfusions?

Receiving a blood transfusion or other products made from blood is safe in the UK as all blood products have been screened for infections such as HIV since 1985.

Giving blood has never been a risk.

Mother-to-baby transmission of HIV ››

‹‹ Back to: HIV transmission through semen and vaginal fluid



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The Information Standard: Certified member

This article was last reviewed on 24/8/2015 by T. Kelaart

Date due for the next review: 23/8/2018

Content Author: R. Scholey

Current Owner: Health promotion

More information:

HIV Transmission Risk Persists During the First 6 Months of Antiretroviral Therapy, Mujugira A1, Celum C, Coombs RW, Campbell JD, Ndase P, Ronald A, Were E, Bukusi EA, Mugo N, Kiarie J, Baeten JM; Partners PrEP Study Team
National Center for Biotechnology Information
US National Library of Medicine
2016 Aug 15;72(5):579-84. doi: 10.1097/QAI.0000000000001019

HIV treatment as prevention and HPTN 052, Cohen MS1, McCauley M, Gamble TR
National Center for Boiotechnology Information
US National Library of Medicine

No one with an undetectable viral load, gay or heterosexual, transmits HIV in the first two years of PARTNER study, Gus Cairns, NAM Aidsmap, March 2014

Viral load and transmission, a factsheet for people with HIV, Gus Cairns, NAM Aidsmap, September 2015

Viral load and transmission, a factsheet for HIV negative people, Gus Cairns, NAM Aidsmap, September 2015

Sexual Activity Without Condoms and Risk of HIV Transmission in Serodifferent Couples When the HIV-Positive Partner Is Using Suppressive Antiretroviral Therapy, Alison J. Rodger, MD; Valentina Cambiano, PhD; Tina Bruun, RN; Pietro Vernazza, MD; Simon Collins; Jan van Lunzen, PhD; Giulio Maria Corbelli; Vicente Estrada, MD; Anna Maria Geretti, MD; Apostolos Beloukas, PhD; David Asboe, FRCP; Pompeyo Viciana, MD1; Félix Gutiérrez, MD; Bonaventura Clotet, PhD; Christian Pradier, MD; Jan Gerstoft, MD; Rainer Weber, MD; Katarina Westling, MD; Gilles Wandeler, MD; Jan M. Prins, PhD; Armin Rieger, MD; Marcel Stoeckle, MD; Tim Kümmerle, PhD; Teresa Bini, MD; Adriana Ammassari, MD; Richard Gilson, MD; Ivanka Krznaric, PhD; Matti Ristola, PhD; Robert Zangerle, MD; Pia Handberg, RN; Antonio Antela, PhD; Sris Allan, FRCP; Andrew N. Phillips, PhD; Jens Lundgren, MD; JAMA. 2016;316(2):171-181. doi:10.1001/jama.2016.5148; Journal of the American Medical Association

Viral load, Michael Carter, Greta Hughson, NAM Aidsmap, March 2014

More confidence on zero risk: still no transmissions seen from people with an undetectable viral load in PARTNER study, Gus Cairns, NAM Aidsmap, July 2016

Hepatitis C, NHS Choices, July 2015

Hepatitis C - Causes, NHS Choices, July 2015

Hepatitis B, NHS Choices, March 2016

Hepatitis B - Factsheet, World Health Organization, Updated July 2016

Michael Carter, Protection of UK blood supply from HIV, HBV, HCV: infected donations rarely enter supply, NAM, (17/6/03)

NAM, Survival outside the body, Aidsmap, (2012)

NAM, Minimising the risk of exposure to blood products and blood-borne viruses, Aidsmap, (2012)

US Department of Health and Human Services, Protect Yourself, Centers for Disease Control and Prevention, (21/6/07)

BHIVA and EAGA, Position statement on the use of antiretroviral therapy to reduce HIV transmission (September 2014)

NHS Choices. HIV and AIDS  2014

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