Identification of #Usutu virus in #blood #donors as part of molecular screening for #WNV, #France, 2023

 

Abstract

BACKGROUND

West Nile Virus (WNV) can be transmitted via blood transfusion and lead to neuroinvasive forms in recipients of blood products.

AIM

We aimed to investigate WNV and Usutu virus (USUV) infections among blood donors in France.

METHODS

Blood donations in 18 of 96 departments of metropolitan France and from travellers returning from affected areas were screened prospectively for WNV using a commercial nucleic acid test (NAT). In addition, stored samples from blood donations in the affected departments were retrospectively tested with RT-qPCR. Differentiation between WNV and USUV infections in NAT-positive samples was done with a RT-qPCR or by seroneutralisation after seroconversion.

RESULTS

Between 18 July and 1 December 2023, 34 (0.018%) of 185,965 blood donation samples were initially positive for WNV. After investigations, 20 donors with USUV infections (16 confirmed, four probable) and five with WNV infections (three confirmed, two probable) were identified. In samples from four donors, WNV and USUV could not be differentiated, and five samples remained indeterminate. Seventeen USUV infections were considered autochthonous: nine departments in the southern and central parts of France, including two departments where WNV was also detected. Infections with USUV were detected between 21 July and 17 October and WNV between 23 August and 20 September.

CONCLUSION

Via screening of blood donations, we could identify the circulation of USUV in 2023 in large parts of metropolitan France. A One Health approach is required to better understand the determinants of USUV circulation in France and the clinical consequences of USUV infections in humans.

Source: Eurosurveillance Weekly, https://www.eurosurveillance.org/

Link: https://doi.org/10.2807/1560-7917.ES.2026.31.43.2600044

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#Netherlands, #WNV detected in a #blood #donor (RIVM, August 17 '26): First case since 2020

 

    A West Nile virus infection has been confirmed in a blood donor in the Netherlands. 

    This occurred in August 2026 during a Sanquin study among blood donors from areas where the West Nile virus had previously been detected in humans, horses, birds or mosquitoes. 

    A laboratory test (PCR) detected the virus in the donor, who had no symptoms and is still not showing any. 

    The person lives in the province of Utrecht and has not been abroad recently. It is therefore likely that the infection was contracted in the Netherlands.

First confirmed case of infection in a human in 2026

    This is the first confirmed case of a human infection in 2026 that originated in the Netherlands. The last time people contracted a West Nile virus infection in the Netherlands was in 2020.

West Nile virus and West Nile fever

    The West Nile virus occurs in birds. 

    The common house mosquito can contract the virus when feeding on the blood of an infected bird. 

    An infected mosquito can then pass the virus on to other birds, to mammals such as horses, and to humans. 

    Humans and horses can fall ill with the West Nile virus, but they cannot pass the virus on to others. 

    The disease caused by the West Nile virus is called West Nile fever. 

    80 per cent of people with West Nile fever have no symptoms, 19 per cent have flu-like symptoms and 1 per cent may develop neurological symptoms. 

    People over 50 and people with weakened immune systems due to illness or medication have a higher risk of becoming very ill from West Nile fever. 

    A small proportion of people who have a severe form of West Nile fever may die.

Mosquitoes capable of transmitting West Nile virus are active

    The fact that, within a short space of time, a horse, a bird and a human have now tested positive for the West Nile virus in different parts of the Netherlands shows that there are mosquitoes active in the Netherlands that carry the West Nile virus. It is still very unlikely for people in the Netherlands to contract West Nile fever.

What can you do to prevent West Nile virus?

    Mosquitoes are mainly active at dusk. To minimise the risk of being bitten, you could, for example:

        § wear clothing that covers the skin (long sleeves, long trousers)

        § keep mosquitoes out (insect screens for windows/doors)

        § use mosquito repellents on exposed skin

        § sleep under a mosquito net

Cooperation and monitoring

    Experts from organisations including the National Institute for Public Health and the Environment (RIVM), the GGDs, Erasmus MC, Royal GD, WBVR, UU, Sanquin and the NVWA are monitoring the situation closely.

Source: 

Link: https://www.rivm.nl/en/news/west-nile-virus-detected-in-a-blood-donor

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