The Risk of West Nile Virus Infection Is Associated with Combined Sewer Overflow Streams in Urban Atlanta, Georgia, USA

Abstract

BackgroundAt present, the factors favoring transmission and amplification of West Nile Virus (WNV) within urban environments are poorly understood. In urban Atlanta, Georgia, the highly polluted waters of streams affected by combined sewer overflow (CSO) represent significant habitats for the WNV mosquito vector Culex quinquefasciatus. However, their contribution to the risk of WNV infection in humans and birds remains unclear.ObjectivesOur goals were to describe and quantify the spatial distribution of WNV infection in mosquitoes, humans, and corvids, such as blue jays and American crows that are particularly susceptible to WNV infection, and to assess the relationship between WNV infection and proximity to CSO-affected streams in the city of Atlanta, Georgia.Materials and methodsWe applied spatial statistics to human, corvid, and mosquito WNV surveillance data from 2001 through 2007. Multimodel analysis was used to estimate associations of WNV infection in Cx. quinquefasciatus, humans, and dead corvids with selected risk factors including distance to CSO streams and catch basins, land cover, median household income, and housing characteristics.ResultsWe found that WNV infection in mosquitoes, corvids, and humans was spatially clustered and statistically associated with CSO-affected streams. WNV infection in Cx. quinquefasciatus was significantly higher in CSO compared with non-CSO streams, and WNV infection rates among humans and corvids were significantly associated with proximity to CSO-affected streams, the extent of tree cover, and median household income.ConclusionsOur study strongly suggests that CSO-affected streams are significant sources of Cx. quinquefasciatus mosquitoes that may facilitate WNV transmission to humans within urban environments. Our findings may have direct implications for the surveillance and control of WNV in other urban centers that continue to use CSO systems as a waste management practice.

Supersuppression: Reservoir Competency and Timing of Mosquito Host Shifts Combine to Reduce Spillover of West Nile Virus

“…2 In Atlanta, Georgia's major urban center, yearly routine mosquito surveillance has consistently demonstrated active WNV infection in Culex mosquitoes. 7 In addition, both passive dead bird surveillance as well as active live bird surveillance have also indicated consistent yearly WNV infection among avian hosts in Atlanta at levels consistent with rates found in other urban centers such as Chicago. [7][8][9][10][11] However, a total of only 330 human cases have been reported in Georgia since 2001 (incidence of 3.3 per 100,000), in contrast to the 2,088 human cases from Illinois since 2002 (incidence of 16.2 per 100,000).…”

“…7 In addition, both passive dead bird surveillance as well as active live bird surveillance have also indicated consistent yearly WNV infection among avian hosts in Atlanta at levels consistent with rates found in other urban centers such as Chicago. [7][8][9][10][11] However, a total of only 330 human cases have been reported in Georgia since 2001 (incidence of 3.3 per 100,000), in contrast to the 2,088 human cases from Illinois since 2002 (incidence of 16.2 per 100,000). 2 With trends in the enzootic infection levels among hosts and vectors in Atlanta similar to those seen in cities with five times the human incidence, the reason for the lack of human WNV spillover in Atlanta and the southeastern region in general has remained unclear.…”

Modifiable Risk Factors for West Nile Virus Infection during an Outbreak—Arizona, 2010

“…breeding and are frequently targeted by WNV vector control programs. 26,27 However, to our knowledge, this is the first time common yard or discarded artificial containers have been identified as a risk for WNV infection during an outbreak. This finding might have been influenced by the arid nature of the study area, making artificial water sources more important as potential larval habitats for Culex spp.…”

Modeling Sewer Overflow of a City with a Large Floating Population

“…Nevertheless, such changes will require political will, considerable financial resources and careful environmental planning. Multimodal analysis was used to estimate associations of the West Nile virus infection in Culex quinquefasciatus, humans, and dead corvids with selected risk factors including the distance to combined sewer overflow streams and catch basins, land cover, median household income, and housing characteristics in Urban Atlanta, Georgia, USA [37]. They referred strongly that combined sewer overflow affected streams are significant sources of Culex quinquefasciatus mosquitoes that may facilitate the West Nile virus transmission to humans within urban environments.…”