Blood Safety for Diseases transmitted via Vectors: The Athens Experience of West Nile Virus

General information

Since 2010, the emergence of West Nile virus (WNV) in Greece has primarily affected the health authorities and secondarily the transfusion services of the country. Through its webpage, the Hellenic Center for Disease Control and Prevention (HCDCP) is providing valuable information on the registered annual number of outbreaks and deaths, mainly concerning the elderly population, and especially those with known co-morbidities.

Infected vectors (mosquitoes) transmit WNV to humans when they bite them. Most people infected with WNV do not experience any signs or symptoms. About 20% of cases present with mild symptoms resembling common influenza (‘flu), and about 1% manifest with more serious symptoms, mainly of the central nervous system. Consequently, the target group of blood donors, i.e. healthy people who are 18-65 years old, might have been either a) infected and developed antibodies without knowing it or b) recently infected and developed ‘flu-like symptoms as a result of WNV after giving blood.

For those blood donors belonging to groups a) and b), the transfusion department must follow certain guidelines in order to check that the collected blood is safe regarding the transmission of WNV. The co-ordination, supervision and writing of protocols followed by the transfusion departments of our country fall under the responsibility of the National Center for Blood Transfusion (EKEA).


Measures taken for blood safety

Temporary exclusion of blood donors who live in areas characterized by qualified authorities as affected by the WNV. This characterization includes areas from which there has been a reported WNV outbreak, diagnosed with the appropriate laboratory tests. These areas change on a daily and annual basis, because the outbreak depends on multiple local factors, such as infected mosquitoes, water stagnation, default seasonal spraying and dense vegetation.

Molecular control of WNV in blood donated in affected areas. The control of transfused blood starts when it is considered necessary by the relevant authorities. This test is not normally included in the obligatory set of tests performed on transfused blood according to guidelines provided by the Ministry of Health. Blood units that have been collected from areas that are afterwards characterized as affected are put into quarantine. This means that they are not transfused until they have undergone molecular control, and are then used or discarded.


Hemovigilance procedures

retrospective control. Blood units collected from any blood donor who develops ‘flu-like symptoms within the next 15 days and WNV infection is diagnosed undergo molecular control. When tests are positive for WNV, the blood donor is informed and the blood units are withdrawn.

If the blood units have already been used, then the patient(s) transfused with red blood cells, plasma or platelets need to be checked.

All infected cases regarding blood donors and patients who have been transfused with WNV-infected blood are reported through a confidential written form to HCDCP’s Co-ordinating Hemovigilance Center (SKAE).

Special measures are taken for blood donors that are not residents but have visited an affected area. These donors are excluded from giving blood for 28 days after they last visited an affected area. If the process of molecular control has already been started, the blood from such donors can be withdrawn and checked immediately.

Blood donors that have been infected by WNV can donate blood 120 days after an established diagnosis and if they are healthy.


Epidemiological data

In Athens in 2010, there were no outbreaks of WNV diagnosed by laboratory tests. Therefore the impact on the transfusion departments in Athens was attributed to the fact that many blood units had been collected from the rest of the country where outbreaks had been recorded. This occurs because of the greater needs of Athenian hospitals for blood units.

In 2010, the first year that WNV emerged in the country, EKEA sent relevant instructions to all the transfusion departments in Athens regarding blood units collected in affected areas (Central Macedonia and Larissa). If blood units had already been transfused, patients were put under surveillance. The instructions also covered blood collection from donors that had visited an affected area outside Athens.

The Consulting Committee of Blood Transfusion sent EKEA a plan of suggested measures to prevent the transmission of WNV infection through blood transfusion. The plan also included measures to ensure a sufficient blood reserve.

In general, Athens was not overburdened by the WNV infection in 2010, unlike Larissa and Central Macedonia prefectures. No WNV transmission via blood or blood products transfusion and no blood donor positive for WNV antibodies was registered in the municipality of Athens.

In May 2011, the supervised services received instructions concerning WNV from the relevant health authorities. At the same time, molecular control of WNV in each area with a registered outbreak was initiated. In August 2011, nucleic acid technology (NAT) molecular control for WNV was started in the three corresponding control centers of Laiko and G. Gennimatas hospitals and EKEA, because of an outbreak in the Marathonas area. No WNV transmission via blood or blood product transfusion and no blood donor positive for WNV antibodies was registered in the municipality of Athens in 2011.

Because of very early recordings of outbreaks in Athens at the beginning of 2012, many blood donors that were inhabitants or worked in the area were excluded. EKEA reported that blood units collected after 1 July 2012 from Nea Smyrni, Palaio Faliro, Agios Dimitrios, Alimos, Elliniko and Argyroupoli had to be retained and sent to EKEA. These measures led to a shortage of blood and blood products, especially platelets, in Athenian hospitals.

The management and handling of blood came under the complete jurisdiction of EKEA, with daily recording of blood reserves in the country, in order to cover the country’s needs. The safety measures taken during blood collection were detailed history taking, the exclusion of a blood donor who worked or lived in an affected area and reporting to the transfusion department any case where the donor developed ‘flu-like clinical symptoms after donating. On 3 August 2012, new areas of Athens were added to the list of affected areas, namely Neos Kosmos, Kynos Argous, METS, Pagrati, Ag. Ioannis (Gouva) and Moschato.

On 4 August, Ilioupoli, Amarousio and Chalandri were registered. Under these circumstances, the ability to cover the blood needs of the hospitals of Athens became extremely difficult. NAT molecular control for WNV started on 21 August at blood centers at EKEA for Athens and AHEPA for Thessaloniki and Alexandroupolis. The municipalities of Piraeus and Oropos were also added to the list of affected areas, minimizing even further the choices for possible donation campaigns and blood collection. On September 2012, due to an extended period of high temperatures, new outbreaks were recorded in the municipalities of Vari, Voula and Vouliagmeni. On 16 November, the safety measures against WNV regarding blood transfusion were withdrawn, without causing serious problems of blood shortage for any patient.

On 2 August 2013, the first registered outbreaks occurred in the outskirts of Athens, in Amarousio, Heraklio, Vrilissia, Pendeli and Chalandri. The exclusion of people living or working in the above mentioned areas immediately created a much greater shortage of blood than the usual shortage that occurs during the summer months in Athens. A week later, on 7 and 9 August, Markopoulo Mesogaias, Rafina and Pikermi were added to the list of affected areas. On 12 August, Agia Paraskevi followed. The shortage of blood started to become apparent, as most campaigns for blood donation in these areas were cancelled. By the end of August blood collection was also restricted from the municipalities of Galatsi, Filothei, Psichiko, Papagou, Cholargos and Glyfada.

At the beginning of September, NAT molecular control for WNV started at three centers in Athens, providing a means of coping with the immense need for blood because of the exclusion of many areas of the capital. After starting the molecular control, Voula, Vari, Vouliagmeni, Lykovrisi and Pefki were added to the affected areas.

On 27 September, a gradual withdrawal of safety measures was started, while on 3 October two more areas were affected, Filadelfia and Chalkidona municipalities.

Continuing high temperatures in Athens could lead to new outbreaks of WNV infection in the city. During the 4 years since the emergence of WNV in Greece, the knowledge and experience gained has made it possible to develop and execute an annual plan for the country’s transfusion departments. The target is to supply the country’s need for blood safely.



The provision of timely updated reports by HCDCP (Department of Epidemiologic Surveillance and Intervention) triggers the implementation of safety measures in the country‘s transfusion departments.

The selection of blood donors following the epidemiologic reports of HCDCP and the guidelines of EKEA leads to the collection of safe blood despite the temporary exclusion of people from affected areas.

NAT molecular testing of blood units from affected areas ensures the safe transfusion of blood and blood products.

The sooner NAT molecular control of blood units is applied, the easier the work of the transfusion departments becomes. Blood units and especially platelets are rapidly released without being put into quarantine.

Blood transport from unaffected areas during exacerbated periods of WNV infection partly covers the need for red blood cells in Athens. Multi-transfused thalassemia patients are transfused sparsely and with older blood units.

Conversely, platelet units become unavailable when molecular control has not been performed on time, and blood donors from affected areas are excluded.

Overall, hemovigilance promotes safe transfusion.

M. Moschou Parara, MD, PhD, Hematologist, Head of Department, Blood Transfusion Establishment, Evaggelismos General Hospital