Socioeconomic and environmental factors associated with dengue fever incidence in Guatemala: Rising temperatures increase dengue risk.

Dengue fever is a mosquito-borne illness that infects 390 million people annually. Dengue outbreaks in Guatemala have been occurring more often and at increased rates since the first dengue outbreak in Guatemala in the 1970s. This study will examine environmental and socioeconomic factors associated with dengue in Guatemala at the municipality (county) level. Socioeconomic factors included population density, Mayan population, economic activity, and attending school. Environmental factors included average minimum annual temperature and annual precipitation. The relationship between environmental and socioeconomic variables and dengue fever incidence was initially evaluated through univariate zero-inflated negative binomial models, and then again through three zero-inflated multivariate negative binomial regression models. For all three models, elevation was considered a predictor of zero-inflation. In the combined model, there was a positive relationship between minimum temperature, economic activity and dengue fever incidence, and a negative relationship between population density, Mayan population and dengue fever. Predicted rates of dengue fever incidence and adjusted confidence intervals were calculated after increasing minimum yearly temperature by 1°C and 2°C. The three municipalities with the highest minimum yearly temperature (El Estor, Iztapa, and Panzós) and the municipality of Guatemala, all had an increase in the magnitude of the risk of dengue fever incidence following 1°C and 2°C increase in temperature. This research suggests that these socioeconomic and environmental factors are associated with risk of dengue in Guatemala. The predicted rates of dengue fever also highlight the potential effect that climate change in the form of increasing temperature can have on dengue in Guatemala.

Temperature Influence on Aedes aegypti Oviposition in the San Joaquin Valley of California.

The establishment and oviposition of Aedes aegypti can vary from one location to another partially due to differing temperature and precipitation. In 2017, Ae. aegypti was first detected in Merced in the Central Valley of California. The objectives of this study were to examine the influence of temperature and precipitation on oviposition of Ae. aegypti, and to determine the beginning and end of the seasonal activity of Ae. aegypti in Merced. The study site consisted of a residential area in the north-east region of Merced where Ae. aegypti was first detected in Merced County. Fifty-four residences were randomly selected as ovitrap sites. Ovitraps were placed at field sites weekly for 12 months, from September 27, 2017, to September 27, 2018. Each week, ovitraps were inspected for the presence of mosquito eggs. Egg counts were used to calculate the following oviposition indices: the ovitrap index (OI) (percent of traps positive) and the egg density index (EDI) (eggs/positive traps). Oviposition occurred primarily from May through October, above a minimum temperature of 10°C, and when almost no rainfall occurred (0.5 mm total). During the year, the percent of positive traps per month ranged from approximately 1.2-67.3%, with highest values in June to October (43.9-67.3%). The highest mean monthly EDI was from July to October (34-44.6) and peaked in October at 44.6 eggs/trap. The EDI values are similar to other locations where Ae. aegypti transmits endemic vector-borne disease. These findings provide baseline data for Ae. aegypti control in Merced and the Central Valley of California.