A One Health view of the West Nile virus outbreak in Andalusia (Spain) in 2020

Figures & data

Figure 1. Localities of mosquito collection marked with empty dots for localities without WNV positive mosquito pools and red dots for the localities where at least one pool has been positive for WNV. A blue dot identifies the locality where an Usutu and several WNV positive pools of Cx. perexiguus were captured and an orange dot the locality where a WNV infected Cx. pipiens and three CxFv infected mosquito pools were captured. Pies indicate the prevalence of WNV (green), USUV (blue) and undetermined flavivirus (orange) antibodies in house sparrows as determined by seroneutralization in 13 localities sampled between July and August 2020, before the detection of WNV human cases, and at three urban localities between September and October 2020 after the outbreak of WNV human cases (localities marked with stars, that correspond from north to south to Palomares del Río, Coria del Río and Puebla del Río). The numbers correspond to the locality names listed in Table 2. Locality 17 corresponds to Cañada de los Pájaros, where only mosquitoes and not house sparrows were captured.

Table 1. Number of mosquitoes captured in BG traps and aspirations in the streets of Coria del Río and Puebla del Río between 25th August and the 2nd December of 2020, after the start of the vector control programmes.

	Coria del Río	Puebla del Río
Anopheles atroparvus	0	84
Culex perexiguus	0	93
Culex pipiens	2	39
Culex theileri	0	4
Aedes caspius	1	6
Total	3	226

Figure 2. Timeline including the dates when human and horse cases were detected [23,54], the dates when first and last positive cases of WNV mosquitoes were found, and the two periods of bird sampling. Figure Created with BioRender.com.

Table 2. Seroprevalence of West Nile virus (WNV), Usutu virus (USUV) or undetermined flavivirus in house sparrows.

	WNV	USUV	Flavivirus	Prevalence
July–August (before human outbreak)
1. Celestino Mutis, Huelva			2.3 (1)	2.3 (43)
2. Corrales, Aljaraque, Huelva	2.1 (1)	6.4 (3)		8.5 (47)
3. Dehesa de Abajo, Puebla del Río, Sevilla	7.1 (3)	2.4 (1)	7.1 (3)	16.7 (42)
4. EDAR – Huelva		2.2 (1)	2.2 (1)	4.4 (45)
5. EDAR – Moguer, Moguer, Huelva	2.3 (1)			2.3 (43)
6. La Hampa, Coria del Río, Sevilla			5 (2)	5 (40)
7. El Palacio, Almonte, Huelva	2.2 (1)	2.2 (1)		4.3 (46)
8. El Rocio, Almonte, Huelva				0 (44)
9. Gibraleón, Huelva	17.5 (7)		10 (4)	27.5 (40)
10. Granja Escuela, Trigueros, Huelva	4.2 (2)	2.1 (1)	6.3 (3)	12.5 (48)
11. Los Alamos, Huelva		7.5 (3)		7.5 (40)
12. La Lagunilla, Palomares del Río, Sevilla				0 (44)
13. Salinas de Punta Umbria			4.1 (2)	4.1 (49)
September–October (after human outbreak)
14. Coria del Río, Sevilla	10.5 (4)		2.6 (1)	13.2 (38)
15. Palomares del Río, Sevilla	5.7 (3)	1.9 (1)	3.8 (2)	11.3 (53)
16. Puebla del Río, Sevilla	11.4 (5)	4.5 (2)	4.5 (2)	20.5 (44)

The overall prevalence of antibodies against flavivirus is indicated together with number of positive individuals and sample size in parenthesis.

Figure 3. Number of female Cx. modestus (orange), Cx. perexiguus (red) and Cx. pipiens (blue) females captured in BG traps baited with CO₂ in 2020: (A) Palacio de Doñana (B) Los Álamos (C) Dehesa de Abajo (D) Cañada de los Pájaros (E) La Hampa.

Figure 4. WNV Infection Rate in Culex perexiguus captured at Dehesa de Abajo (triangles and dotted line) and Cañada de los Pájaros (points and continuous line) between July and December 2020.

Table 3. Seroprevalence of West Nile virus (WNV), Usutu virus (USUV) or undetermined flavivirus (Flavivirus) antibodies in different avian species captured in the urban areas of three different villages after the 2020 West Nile virus human outbreak in Andalusia.

Avian species	WNV	USUV	Flavivirus	Prevalence
Bubulcus ibis	100 (1)			100 (1)
Columba livia	100 (1)			100 (1)
Estrilda astrild				0 (1)
Ficedula hypoleuca				0 (3)
Passer domesticus	8.9 (12)	2.2 (3)	3.7 (5)	14.8 (135)
Streptopelia decaocto	20 (1)		20 (1)	40 (5)
Sturnus unicolor		25 (1)		25 (4)
Turdus merula	40.9 (9)	18.2 (4)	31.8 (7)	90.9 (22)
Upupa epops			100 (1)	100 (1)

The overall prevalence of antibodies against flavivirus is indicated together with number of positive individuals and sample size in parenthesis.

García San Miguel Rodríguez-Alarcón L, Fernández-Martínez B, Sierra Moros MJ, et al. Unprecedented increase of West Nile virus neuroinvasive disease, Spain, summer 2020. Euro Surveill. 2021;26:19.

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Junta de Andalucía: Fiebre del Nilo Occidental of Encefalitis del Oeste del Nilo o West Nile virus. Junta de Andalucía [cited 2022 Sept 19]. Available from: https://www.juntadeandalucia.es/organismos/agriculturapescaaguaydesarrollorural/areas/ganaderia/sanidad-animal/paginas/fiebre-nilo-occidental.html.

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Data availability statement

The data that support the findings of this study are available from the corresponding author, JF, upon reasonable request.