● Human immunodeficiency virus (HIV) 1 and 2:
The risk of developing HIV disease/AIDS after being transfused with HIV infected blood is high (greater than 95%). All donor blood must be screened for antibody to HIV-1 and HIV-2 using a sensitive test. Transmission of HIV in donor blood can be minimized by using low risk voluntary unpaid donors and giving donors the opportunity to self-exclude when they suspect infection with HIV.
Even when an HIV antibody screening test is negative, blood may still contain HIV. This can happen when blood is collected during the ‘window period’, i.e. soon after a donor becomes infected with HIV when antibody to the virus is
not yet detectable in the serum.
● Hepatitis B virus (HBV):
Those at greatest risk of developing viral hepatitis from HBV infected blood
and blood products are young children and
those without effective immunity. Tests to screen donor blood for HBV are based on the detection of hepatitis B surface antigen (HBsAg).
● Hepatitis C virus (HCV).
This can cause viral hepatitis in recipients but it is not as infectious as HBV. Following acute infection, 70–80% of individuals become chronic HCV carriers with the
risk of developing liver cirrhosis and liver cancer later in life. Information on the epidemiology of HCV in tropical countries is incomplete. Where the prevalence of HCV is known to be high, donor blood should be screened for antibody to HCV when this can be afforded.
● Treponema pallidum
Transfusing blood containing T. pallidum can cause syphilis in recipients but
the risk of transmitting the disease is low, particularly when donated blood is stored at 2–8 C for 48–72 h which inactivates T. pallidum.
● Plasmodium species
Transfusing blood containing malaria parasites can cause malaria in recipients without effective immunity, e.g. young
children and pregnant women. Blood should not be collected from donors with suspected malaria.
In malaria endemic areas it is not feasible to screen all donor blood for malaria parasites or reject donors who have had malaria previously. In some malaria endemic areas, it is the policy to give curative antimalarial drugs followed by prophylactic drugs for 3 weeks to all recipients of blood. Tests to detect malaria parasites in blood and rapid antigen tests to diagnose malaria are available.
● Trypanosoma cruzi:
Transfusing blood containing
T. cruzi can cause Chagas’ disease
T. cruzi is endemic in South and Central American countries from Mexico to Argentina. Donors infected with
T. cruzi are often asymptomatic and therefore in endemic areas, donor blood must be screened for T. cruzi. Guidelines regarding the most appropriate test to use in a particular area should be obtained from the nearest Chagas’ Disease
Reference Laboratory or regional blood transfusion.
● Human T cell lymphotropic virus (HTLV)1
This virus can cause HTLV disease, adult T-cell leukaemia/lymphoma (ATLL), or tropical spastic paraparesis (TSP). It has a high prevalence in parts of Central and South America, the Caribbean, and parts of sub-Saharan Africa. It is estimated that about 60% of recipients receiving HTLV infected blood actually seroconvert. The risk of developing disease later in life is thought to be low. HTLV antibody screening tests are expensive.
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