Viral infections

In accordance with regulations, every blood donation is systematically screened for the agents responsible for the following diseases: AIDS, hepatitis B, hepatitis C, syphilis, and HTLV-associated diseases (only for new donors in metropolitan France and all donors in the French departments of the Americas).

Regulations require routine screening of every blood donation for biological markers of viral infections caused by HIV (anti-HIV-1/2 antibodies and Viral Genomic Screening (VGS) for HIV-1), HTLV I-II (anti-HTLV I-II antibodies) (for new donors in metropolitan France only), hepatitis B virus (anti-HBc antibodies, HBs antigen, and HBV VGS), and hepatitis C virus (anti-HCV antibodies and HCV VGS). The causative agent of syphilis (Treponema pallidum) is screened for in every donation using a serological test (TPHA). The DGV technique, implemented on July 1, 2001, for HIV-1 and HCV and in 2010 for HBV, makes it possible to detect very recent infections, even before antibodies or viral antigens are detectable by serological tests. It reduces the window period: 9 days on average for HIV-1 (compared to 22 days with conventional serological tests), 7 days for HCV (compared to 66 days), and 22 days for HBV (compared to 38 days).

Parasitic infections

Routine screening for viral infections may be supplemented, depending on risk factors identified during the pre-donation interview (history of travel, birth in an endemic area), by testing for antibodies against the parasites responsible for malaria (various species of Plasmodium) and/or Chagas disease (Trypanosoma cruzi).

Malaria is a parasitic disease caused by a blood parasite of the genus Plasmodium, transmitted to humans by a mosquito (genus Anopheles). Traditionally, four species of the genus Plasmodium are responsible for the disease in humans: P. falciparum, P. vivax, P. ovale, and P. malariae. Recently, a fifth species, P. knowlesi, responsible for monkey malaria, has been described as a human infection causing quartan fever. All Plasmodium species can be transmitted through transfusion, and infection can occur with a very small number of parasites.

Malaria

Prevention of transfusion-transmitted malaria relies on medical donor screening and testing for antimalarial antibodies. Questioning of donors by the physicians responsible for blood collection (following criteria established in the decree of April 5, 2016) allows for the identification of at-risk donors: nationals of endemic countries or individuals who have traveled to a malaria-endemic area. Exclusion from donation for 4 months following return from an endemic country is supplemented, at the next donation, by serological screening. The risk of contracting P. falciparum malaria more than 4 months after returning from an endemic area is approximately 1%.

There is no assessment in France of the residual risk of malaria transmission analogous to that described for viruses subject to routine screening. Nevertheless, published data show that, thanks to the preventive measures implemented, the risk of post-transfusion malaria has fallen from 1 case per million about twenty years ago to 0.2–0.5 cases per million units transfused today. In France, over the past fifteen years, four cases of transfusion-transmitted malaria have been reported: one in 2002, one in 2006, one in 2012, and one in 2015. The first three were caused by P. falciparum, and the last by P. malariae.

Chagas Disease

Prevention of the risk of transfusion-transmitted Trypanosoma cruzi, the parasite responsible for Chagas disease, relies on two measures: systematic screening since May 2007 for anti-Trypanosoma cruzi antibodies in at-risk blood donors, and the exclusion from blood donation of any donor who has returned from an endemic country (Latin America) within the past 4 months. The risk criteria are as follows: donors who have lived in or were born in an endemic country, and donors whose mother is from an endemic country.

A study conducted by the EFS between May 2007 and December 2008 shows that the prevalence of Chagas disease is low in France: 5 donations tested positive out of 32,748 at-risk donors tested.

For other blood-borne pathogens

Certain infectious agents are not routinely screened for but may, under specific epidemiological circumstances (clustered cases, epidemics, etc.), pose a blood safety concern that warrants the use of preventive measures. This is particularly the case for agents causing acute infections such as hepatitis A, toxoplasmosis, dengue, leptospirosis, chikungunya, West Nile virus, and Zika virus—all of which are blood-borne. In the specific case of West Nile virus, dengue, chikungunya, and Zika, a Decision Support Unit (DSU) for “human body components and products,” established in 2005, is activated if the circulation of these viruses is detected in France, Europe, or worldwide. This CAD proposes measures to be implemented to ensure the safety of labile blood products and transplants (organs/tissues/cells). Until the first quarter of 2019, the CAD was activated at the initiative of the ANSM. As of April 2019, it is now overseen by the High Committee for Public Health.

Since no test is available for the biological screening of donations for prion infections, transfusion risk prevention is achieved by excluding donors with a family history of neurodegenerative disease or who have received treatment with extracted growth hormones or who have undergone certain transplants (dura mater or cornea). Screening was tightened in 1997 with the exclusion of donors who had previously received a blood transfusion, and in 2001 with the exclusion of donors who had spent a cumulative total of more than one year in the United Kingdom between 1980 and 1996, a period of risk due to the bovine spongiform encephalopathy (BSE) epidemic in that country.
The latest estimates of the transfusion risk associated with variant Creutzfeldt-Jakob disease (vCJD) were conducted by Afssaps in 2007. This risk was estimated at 1 in 360,000 donations in France and 1 in 50,000 in the United Kingdom. To date, four cases of vCJD transmission via transfusion have been reported in the United Kingdom and none in France.
Similarly, in France, no cases of transmission linked to transfusions of labile blood products from patients who died of other types of CJD (sporadic, genetic, or iatrogenic) have been reported.
In 2010, Santé publique France and Inserm conducted a study to estimate the annual number of blood donors likely to be in the preclinical phase of sporadic CJD (sCJD), based on several assumptions regarding the duration of blood infectivity prior to the onset of clinical symptoms. The authors conclude that this number is low. This finding, along with the lack of a global increase in the number of sporadic CJD cases over time, supports the conclusion that the risk of sporadic CJD transmission via transfusion, if it exists at all, is very low.