associated with drought is West Nile virus (WNV) disease (Davis et al., 2018; Johnson & Sukhdeo, 2013; Paull et al., 2017; Ruiz et al., 2010). Culex pipiens —the main WNV vector in the U.S. and Italy—has a higher dehydration tolerance than most insects, including other mosquitoes; they can tol- erate up to 40% water loss. This resistance to dehydration facilitates increased Culex populations following drought (Benoit & Denlinger, 2007). Furthermore, dehydration in Culex mosquitoes increases activity and biting rates, amplifying the risk of disease transmission (Hagan et al., 2018). These behaviors differentiate Culex mosquitoes from other vectors and facilitate the amplifi- cation of diseases vectored by Culex mosqui- toes in drought conditions. Vector–pathogen dynamics also facili- tate the relationship between WNV and drought. The higher temperatures that often accompany drought increase WNV titers in mosquitoes, shorten WNV incuba- tion time, and increase the amount of virus transmitted from vectors to hosts (Reisen et al., 2006). Similarly, higher temperatures increase mosquito WNV infection rates (Kilpatrick et al., 2008). Combined with the dehydration resistance and drought- time behavior of the Culex vector, WNV dynamics during drought facilitate the amplification of WNV transmission. Drought also exacerbates poverty. Several social and economic determinants of health, including nutrition and migration, drive this complicated problem. Indeed, for already- impoverished groups living on the edge of subsistence, drought can bring additional dis- tress, even devastation (Landes, 1999). Many agricultural communities depend on locally cultivated crops and livestock for nutritional content. When drought decreases crop yields, subsistence agriculturists face food insecu- rity (Brewis et al., 2020; Lieber et al., 2020). Decreased water availability also inhibits food preparation and safety while diverting income from food acquisition to water acqui- sition (Brewis et al., 2020). Through these mechanisms, drought increases short-term effects of malnutrition such as lower body mass, especially in children (Jankowska et al., 2012; Lieber et al., 2020). Long-term effects, such as child wasting or stunting, can also increase following drought periods (Hagos et al., 2014; Jankowska et al., 2012; Yeboah et
FIGURE 1
The Po River Basin in Northern Italy
Source: Food and Agriculture Organization of the United Nations and Esri.
cipitation and El Niño–Southern Oscillations facilitates the growth of Coccidioides myce- lia (Tobin et al., 2022; Weaver & Kolivras, 2018). Subsequent periods of high tempera- tures and drought then dry the soil, increas- ing the risk of soil disturbance and transmis- sion (Head et al., 2022). Thus, within-year variability of precipitation increases the transmission of Valley fever, contributing to the public health burden of drought-related air pollution (Shriber et al., 2017). In addition to reducing soil moisture, drought alters surface water availability, increasing the risk of chemical contamina- tion. Drought-associated floods introduce nonpoint source nitrogen and phosphorus
pollution via runoff (Bi et al., 2019). Simi- larly, groundwater depletion during droughts increases nitrate concentrations in private wells, which are a critical water infrastruc- ture in rural communities (Levy et al., 2021). This nitrate contamination can result in inad- equate blood oxygenation levels in infants and occasionally fatal methemoglobinemia (Maxwell, 2013). Drought-associated chemi- cal contamination of surface and groundwa- ter thus presents a severe public health threat, especially in rural areas. Drought-driven declines in surface water availability also impact the ecology and epidemiology of mosquito-borne diseases. The most well-evidenced zoonotic disease
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June 2025 • Journal of Environmental Health
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