Cytomegalovirus (CMV)

A very common virus which causes a mild ‘flu-like’ illness. Individuals in good health make a full recovery and are usually unaware of the infection. We may test for antibodies against the virus. A positive test indicates that the individual has had CMV infection and may still have the virus. Having antibodies to CMV is of no significance to the health of the donor. However, for some patients with a poor immune system (particularly small babies), CMV can cause a life-threatening illness. CMV-positive blood is safe for most patients, and donors are not informed of a positive result.

Trypanosoma cruzi (T.cruzi)

Trypanosoma cruzi is a parasite (often abbreviated to T.cruzi), found in certain parts of Central and South America. It is transmitted to humans by biting insects or from mother to baby at the time of birth, or by blood transfusion. Over many years, the parasite can cause damage to the muscles in the heart and intestines, leading to an illness called Chagas disease. Not all infected people become ill. Our tests look for antibodies to the infection. A donor’s place of birth and travel history determine whether the test is required.


Caused by parasites which are transmitted by the bites of mosquitoes. The infection causes fever and is a major cause of death in some parts of the world. We test for antibodies to the malaria parasites. A confirmed positive result does not necessarily mean that the individual has active malaria, merely that they have had malaria at some time.


Caused by a bacterium called Treponema pallidum. This family of bacteria can also cause tropical diseases called Yaws and Pinta. Syphilis is usually a sexually transmitted infection which, if untreated, can cause serious disease. Yaws and Pinta cause skin and joint problems. All three diseases are fully treatable with antibiotics. The tests we use look for specific antibodies to the bacterium. These antibodies remain in a person’s blood many years after the infection has gone. A positive test for syphilis often relates to an infection in the past, but we are not able to use blood as long as the test is positive.

Hepatitis B virus (HBV)

Hepatitis B is a liver infection caused by the Hepatitis B Virus. The virus is most commonly transmitted from mother to child during birth and delivery, as well as through contact with blood or other body fluids during sex with an infected partner, unsafe injections or exposures to sharp instruments.

Hepatitis B often does not cause any obvious symptoms in adults, and typically passes in a few months without treatment.

Hepatitis B is common in many parts of the world including South and South-East Asia, the Middle and Far East, southern Europe and Africa, but it is less common in Northern Ireland.

Testing for Hepatitis B

All blood donations are routinely tested for tested for Hepatitis B as well as Hepatitis C, Hepatitis E, HIV, HTLV and Syphilis.

How do you test for Hepatitis B?

  • Since 1972, we have tested blood donors for Hepatitis B surface antigen (HBsAg). This is the protein which coats the virus.
  • In 2010, we also began testing for Hepatitis B DNA, the genetic code of the virus itself. This increased our ability to detect donors with active Hepatitis B.
  • On 30th May 2022, we started testing all donors for anti-Hepatitis B core (anti-HBc) antibodies. This additional test was recommended by SaBTO (The Advisory Committee on the Safety of Blood, Tissues, and Organs) so as to identify donors who have previously had Hepatitis B.


What happens after you test my blood?

Donors with negative results

Most donors have negative Hepatitis B test results and hear no more from us (we only get in touch if your Hepatitis B test is positive). If all test results are satisfactory, we can use your gift to treat patients and you can keep giving blood.

  • False reactions

On occasion, the tests used in NIBTS will produce false positive results. Because of our operational procedures, NIBTS cannot use a donation if it gives a false reaction. If a donor’s blood causes a false reaction, we will write to let you know. The false reaction does not mean that there is anything wrong with your health, and there is no need for you to see a doctor or have any additional tests. You will be able to donate again once the reaction has cleared, and we will check this by taking samples rather than a full donation when you next come to give blood.

Donors with positive results

  • Active Hepatitis B

We rarely find donors with positive HBsAg and Hepatitis B DNA results. If we do, our medical team will get in touch to tell you your results, what they mean for you, and what needs to happen next. They will ask permission to tell your GP, and to refer you to appropriate follow-up services. They will also give you information which helps to explain your test results and diagnosis. NIBTS is required by law to notify Public Health whenever anyone is diagnosed with Hepatitis B. Unfortunately, you will no longer be able to give blood.

  • Previous Hepatitis B

We expect that only a small number of donors will have had previous Hepatitis B infection. Most people who have anti-HBc antibodies will have cleared Hepatitis B; have undetectable levels of virus in their bloodstream; and will have experienced no symptoms.

If you are found positive for anti-HBc antibodies, our medical team will get in touch to tell you your results, and what they mean for you. They will also ask permission to tell your GP.

You won’t need any routine medical reviews or treatment as you no longer have active infection. However, you will no longer be eligible to give blood. This decision has been made to allow us to begin the complex testing programme promptly and safely and may be reviewed in the future.

The Northern Ireland Blood Transfusion Service’s priorities are providing a safe blood supply for patients, and a safe experience for donors, and we constantly strive to improve both. The patients who receive your gift cannot thank you themselves, so on their behalf, thank you.

Human immunodeficiency virus (HIV)

If untreated, affects the immune system with the development of Acquired Immune Deficiency Syndrome (AIDS). The HIV virus is transmitted sexually, can be passed from mother to baby, and by intravenous drug use. Once an individual becomes infected with HIV, the virus remains in the body. A person who has HIV does not necessarily have AIDS. We perform two tests for the virus; one is a combination test that looks for both a protein in the virus coat and antibody to the virus; and a second that looks for the virus itself, targeting the virus nucleic acid. If either or both of the tests are reactive, further tests are done to confirm the result. Unlike many other infections the antibodies produced do not protect against the virus.

Hepatitis C virus (HCV)

Like hepatitis B, infects the liver and can cause inflammation and liver damage. The virus is commonly transmitted by needles, and thus may be associated with injecting drug use. Like HIV, HCV can persist in the body even when antibodies are present. We perform two tests for the virus, one that looks for antibody to the virus, and a second that looks for the virus itself, targeting the virus nucleic acid. If either or both of the tests are reactive, further tests are done to confirm the result. Like HIV, the antibodies produced do not protect against the virus. Many of the donors we identify have had the virus for years and feel completely well.

Hepatitis E Virus (HEV)

Both animals and humans can be infected. HEV infection usually causes no symptoms, if it does cause symptoms they are generally mild. Normally the virus infection will clear by itself. However, it is known that patients whose immune system is suppressed (eg chemotherapy or transplant patients) can have a more serious illness if they contract Hepatitis E. You will be informed if the virus is found in your donation.

Donors cannot donate until at least 6 months have passed since recovery from Hepatitis E infection.  Alternatively, if a blood test taken when a donor feels fully recovered shows clearance of the virus nuclei acid and the development of immune antibodies then they can donate again before this 6 month period.

Human T-lymphotropic virus (HTLV)

A virus which infects white cells called T-lymphocytes. Like HIV, the HTLV virus remains in the body once an individual is infected, even though antibodies develop. Most people who are infected with the virus are perfectly well and never have any illness. Occasionally, it can cause a neurological disorder called Tropical Spastic Paraparesis (or HTLV Associated Myelopathy) or a blood disease called Adult T-cell Leukaemia. These diseases are very rare.

The infection is found most commonly in people from Japan, the West Indies and parts of the Middle East. The virus is commonly transmitted from mother to child by breast feeding, but is also passed on by sexual contact or by intravenous drug use. We screen for antibodies against HTLV, and if the test is reactive further tests are performed to confirm the result.