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The risk of tick-borne encephalitis virus transmission via substances of human origin
Assessment
2 Oct 2024
This report aims to assess the available evidence on the risk of tick-borne encephalitis virus (TBEV) transmission through substances of human origin (SoHO) such as blood, organs, tissues, and cells, and proposes potential safety measures.
Executive summary
Tick-borne encephalitis (TBE) is a viral infection transmitted primarily through tick bites or consumption of unpasteurised dairy products from infected livestock. It represents a growing public health concern in Europe, with thousands of cases reported annually in eastern and central Europe, and parts of Asia. This report aims to assess the available evidence on the risk of tick-borne encephalitis virus (TBEV) transmission through substances of human origin (SoHO) such as blood, organs, tissues, and cells, and proposes potential safety measures. The target audience for this document is professionals in the European Union/European Economic Area (EU/EEA) working in SoHO establishments, and other professionals involved in SoHO donor selection.
TBE is a notifiable disease in the EU/EEA, with 28 680 confirmed cases reported during the period 2013−2022, most being locally-acquired autochthonous cases. The mean notification rate in EU/EEA countries during this period ranged from 0.01 to 16.83 per 100 000 population. Cases peak during April−November, coinciding with tick activity and outdoor human activities. More than two-thirds of TBEV infections remain asymptomatic, though the exact proportion is uncertain as mild clinical illness is not often diagnosed. Symptomatic cases generally present as a biphasic disease with an initial flu-like phase followed by a second phase characterised by inflammation of the central nervous system. The case-fatality of TBE is below 2%, generally reported at 0.5%. However, long-term sequelae have been reported in 10−40% of patients with neurological symptoms.
TBEV transmission through SoHO is documented but rare, with two cases reported via transfusion from one donor and three cases via organ transplant from another donor.
Reports of transmission are rare despite important TBE notification rates in endemic areas and non-trivial seroprevalence among blood donors. This suggests a very low likelihood of transmission of TBEV leading to symptomatic disease through blood transfusion. The impact of transmission of TBEV through blood transfusion is unknown and the risk of transmission of TBEV through blood transfusion in EU/EEA cannot be assessed.
Transmission of TBEV through organ transplantation has been reported from one donor and all recipients of organs procured from the infected donor were infected by TBE. The likelihood of transmission of TBEV leading to symptomatic disease through organ transplantation is considered low. The severity of the disease course may be associated with immunosuppression, however it is important to note that no specific antiviral treatments are available for TBEV. The impact of a transmission of TBEV through organ transplantation is considered moderate.The risk of TBEV transmission through organ transplantation in the EU/EEA is considered low.
In the absence of reported cases of TBEV transmission through tissue or cell transplantation, the likelihood and impact are unknown, and the risk for these SoHOs cannot be assessed.
Potential measures during TBEV transmission periods could include deferring blood donors reporting recent tick bites in affected areas for a period of 28 days; testing organ, tissue and cell donors for TBEV ribonucleic acid (RNA) and TBEV antibodies, and identifying exposure risks in order to inform the transplant team. A TBEV infection should be considered for recipients of organs, tissues, or cells who exhibit neurological symptoms if the donor had a risk of exposure to TBEV. Increasing vaccination rates in highly endemic areas could improve overall SoHO safety in relation to TBEV.
There are still several areas of uncertainty in relation to TBE and the risk of TBEV infection through SoHO, including the infectious dose and viraemia levels in asymptomatic individuals.
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The risk of tick-borne encephalitis virus transmission via substances of human origin - EN - [PDF-2.43 MB]
...
Assessment
2 Oct 2024
This report aims to assess the available evidence on the risk of tick-borne encephalitis virus (TBEV) transmission through substances of human origin (SoHO) such as blood, organs, tissues, and cells, and proposes potential safety measures.
Executive summary
Tick-borne encephalitis (TBE) is a viral infection transmitted primarily through tick bites or consumption of unpasteurised dairy products from infected livestock. It represents a growing public health concern in Europe, with thousands of cases reported annually in eastern and central Europe, and parts of Asia. This report aims to assess the available evidence on the risk of tick-borne encephalitis virus (TBEV) transmission through substances of human origin (SoHO) such as blood, organs, tissues, and cells, and proposes potential safety measures. The target audience for this document is professionals in the European Union/European Economic Area (EU/EEA) working in SoHO establishments, and other professionals involved in SoHO donor selection.
TBE is a notifiable disease in the EU/EEA, with 28 680 confirmed cases reported during the period 2013−2022, most being locally-acquired autochthonous cases. The mean notification rate in EU/EEA countries during this period ranged from 0.01 to 16.83 per 100 000 population. Cases peak during April−November, coinciding with tick activity and outdoor human activities. More than two-thirds of TBEV infections remain asymptomatic, though the exact proportion is uncertain as mild clinical illness is not often diagnosed. Symptomatic cases generally present as a biphasic disease with an initial flu-like phase followed by a second phase characterised by inflammation of the central nervous system. The case-fatality of TBE is below 2%, generally reported at 0.5%. However, long-term sequelae have been reported in 10−40% of patients with neurological symptoms.
TBEV transmission through SoHO is documented but rare, with two cases reported via transfusion from one donor and three cases via organ transplant from another donor.
Reports of transmission are rare despite important TBE notification rates in endemic areas and non-trivial seroprevalence among blood donors. This suggests a very low likelihood of transmission of TBEV leading to symptomatic disease through blood transfusion. The impact of transmission of TBEV through blood transfusion is unknown and the risk of transmission of TBEV through blood transfusion in EU/EEA cannot be assessed.
Transmission of TBEV through organ transplantation has been reported from one donor and all recipients of organs procured from the infected donor were infected by TBE. The likelihood of transmission of TBEV leading to symptomatic disease through organ transplantation is considered low. The severity of the disease course may be associated with immunosuppression, however it is important to note that no specific antiviral treatments are available for TBEV. The impact of a transmission of TBEV through organ transplantation is considered moderate.The risk of TBEV transmission through organ transplantation in the EU/EEA is considered low.
In the absence of reported cases of TBEV transmission through tissue or cell transplantation, the likelihood and impact are unknown, and the risk for these SoHOs cannot be assessed.
Potential measures during TBEV transmission periods could include deferring blood donors reporting recent tick bites in affected areas for a period of 28 days; testing organ, tissue and cell donors for TBEV ribonucleic acid (RNA) and TBEV antibodies, and identifying exposure risks in order to inform the transplant team. A TBEV infection should be considered for recipients of organs, tissues, or cells who exhibit neurological symptoms if the donor had a risk of exposure to TBEV. Increasing vaccination rates in highly endemic areas could improve overall SoHO safety in relation to TBEV.
There are still several areas of uncertainty in relation to TBE and the risk of TBEV infection through SoHO, including the infectious dose and viraemia levels in asymptomatic individuals.
Download
The risk of tick-borne encephalitis virus transmission via substances of human origin - EN - [PDF-2.43 MB]
...