NASA has recently confirmed that the summer of 2023 was the hottest in history (O’Shea, 2023). The record-breaking air temperatures and the unprecedented disappearance of Antarctica’s ice are clear indications of intensifying global warming, which is altering climatic zones around the planet. As a result, diseases traditionally associated with the tropics are beginning to spread in Europe. Six autochthonous (non-travel related) dengue virus cases have been reported in Europe between July and August 2023: four in Italy and two in French territory. Unfortunately, as the conditions for the vector of this disease, Aedes albopictus and Aedes aegypti, are now- favourable in multiple European countries, the Dengue virus is more likely to spread throughout the old continent (European Centre for Disease Prevention and Control, Dengue worldwide overview, 2023b).
A vaccine is not yet available for most flavivirus diseases; hence, vector control and accessible, reliable diagnostics are central to limiting the spread of those arboviral infections. The Native Antigen Company offers an extensive range of flavivirus antigens, including the bestselling Dengue serogroups 1-4 VLPs (virus-like particles), enabling the development of next-generation diagnostic assays.
Favourable vector conditions
Historically, Dengue and other flavivirus cases were associated with northern world citizens travelling to the tropics and not protecting themselves sufficiently from mosquito bites. These viraemic travellers pose a significant threat to areas of Europe where the known disease vectors are established. Aedes albopictus is now listed as one of the top 100 invasive species, particularly in contrast to the other known vector of Dengue Aedes aegypti, it shows signs of adaptation to colder climates. This ecological plasticity, coupled with climate change, – facilitates the spread of this mosquito species across a large part of Europe, while Aedes aegypti is established most notably around the Black Sea and in Cyprus (European Centre for Disease Prevention and Control, Aedes albopictus – factsheet for experts 2016).
Figure 1. Distribution of Aedes albopictus; vector of Dengue Virus in Europe as of August 2023. Picture source: European Centre for Disease Prevention and Control, Aedes albopictus – current known distribution: August 2023a.
Flavivirus problem in Europe
Unfortunately, as shown on the map in Figure 1 (above), flavivirus vector surveillance in many parts of the continent is still lacking. The only way to estimate the burden of Dengue and other flavivirus diseases is to introduce efficient surveillance systems and vector studies, especially since most people infected with the dengue virus show mild symptoms or are asymptomatic (World Health Organization, 2023).
Earlier this year, we were writing about increased diagnostic surveillance in parts of England where another flavivirus disease, Tick-borne encephalopathy, has been detected or suspected in the past (link to the blog article here: Tick-born encephalopathy virus (TBEV) resurgence and increased diagnostic surveillance. – The Native Antigen Company). Since the locally acquired dengue fever cases have been reported in Lombardy and Lazio regions (EpiCentro, Arbovirosi 2023), Italian public health authorities also introduced response and control measures, including serological testing in at-risk areas (Cassaniti et al., 2014).
Italy has also reported an increase in West Nile virus infections, another flavivirus. As of September 13, 2023, there have been 203 reported cases of WNV infection this transmission season. The second most significant number of West Nile cases has been reported in Greece this summer: 199 human cases, including 14 deaths caused by the virus. Moreover, since June of this year, autochthonous human cases of WNV infection have been reported for the first time in Gironde, Charente-Maritime and Alpes-Maritimes in France, Kastoria in Greece and Huelva and Valencia/València in Spain (European Centre for Disease Prevention and Control, Weekly updates: 2023 West Nile Virus Transmission season, 2023c).
Figure 2. Distribution of West Nile Virus infections in comparison to previous years in Europe. Picture source: European Centre for Disease Prevention and Control, West Nile virus – human cases compared to previous seasons,2023d.
The Native Antigen Company offers an extensive range of flavivirus antigens, expressed as recombinant proteins in our mammalian expression system, insects’ cells as well as virus-like particles. For more information about our comprehensive flavivirus portfolio refer to our flavivirus products factsheet here: Flavivirus products fact sheet.pdf (thenativeantigencompany.com).
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References
Cassaniti, I. et al. (2014) Preliminary results on an autochthonous dengue outbreak in Lombardy region, Italy, August 2023, Eurosurveillance. Available at: https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2023.28.37.2300471 (Accessed: 15 September 2023).
EpiCentro (no date) Arbovirosi, Arbovirosi news. Available at: https://www.epicentro.iss.it/arbovirosi/aggiornamenti (Accessed: 15 September 2023).
European Centre for Disease Prevention and Control (2016) Aedes albopictus – factsheet for experts, European Centre for Disease Prevention and Control. Available at: https://www.ecdc.europa.eu/en/disease-vectors/facts/mosquito-factsheets/aedes-albopictus (Accessed: 15 September 2023).
European Centre for Disease Prevention and Control (2023a) Aedes albopictus – current known distribution: August 2023, European Centre for Disease Prevention and Control. Available at: https://www.ecdc.europa.eu/en/publications-data/aedes-albopictus-current-known-distribution-august-2023 (Accessed: 15 September 2023).
European Centre for Disease Prevention and Control (2023b) Dengue worldwide overview, European Centre for Disease Prevention and Control. Available at: https://www.ecdc.europa.eu/en/dengue-monthly (Accessed: 15 September 2023).
European Centre for Disease Prevention and Control (2023c) Weekly updates: 2023 West Nile Virus Transmission season, European Centre for Disease Prevention and Control. Available at: https://www.ecdc.europa.eu/en/west-nile-fever/surveillance-and-disease-data/disease-data-ecdc (Accessed: 15 September 2023).
European Centre for Disease Prevention and Control (2023d) West Nile virus – human cases compared to previous seasons, 13 September 2023, European Centre for Disease Prevention and Control. Available at: https://www.ecdc.europa.eu/en/publications-data/west-nile-virus-human-cases-compared-previous-seasons-13-september-2023 (Accessed: 15 September 2023).
O’Shea, C. (2023) NASA announces Summer 2023 hottest on record, NASA. Available at: https://www.nasa.gov/press-release/nasa-announces-summer-2023-hottest-on-record (Accessed: 15 September 2023).
World Health Organization (no date) Dengue and severe dengue, World Health Organization. Available at: https://www.who.int/news-room/fact-sheets/detail/dengue-and-severe-dengue (Accessed: 15 September 2023).