High Rate of Non-Human Feeding by Aedes aegypti Reduces Zika Virus Transmission in South Texas.

Mosquito-borne viruses are emerging or re-emerging globally, afflicting millions of people around the world. Aedes aegypti, the yellow fever mosquito, is the principal vector of dengue, Zika, and chikungunya viruses, and has well-established populations across tropical and subtropical urban areas of the Americas, including the southern United States. While intense arboviral epidemics have occurred in Mexico and further south in the Americas, local transmission in the United States has been minimal. Here, we study Ae. aegypti and Culex quinquefasciatus host feeding patterns and vertebrate host communities in residential environments of South Texas to identify host-utilization relative to availability. Only 31% of Ae. aegypti blood meals were derived from humans, while 50% were from dogs and 19% from other wild and domestic animals. In Cx. quinquefasciatus, 67% of blood meals were derived from chicken, 22% came from dogs, 9% from various wild avian species, and 2% from other mammals including one human, one cat, and one pig. We developed a model for the reproductive number, R0, for Zika virus (ZIKV) in South Texas relative to northern Mexico using human disease data from Tamaulipas, Mexico. We show that ZIKV R0 in South Texas communities could be greater than one if the risk of human exposure to Ae. aegypti bites in these communities is at least 60% that of Northern Mexico communities. The high utilization of non-human vertebrates and low risk of human exposure in South Texas diminishes the outbreak potential for human-amplified urban arboviruses transmitted by Ae. aegypti.

Surveillance for Flaviviruses Near the Mexico-U.S. Border: Co-circulation of Dengue Virus Serotypes 1, 2, and 3 and West Nile Virus in Tamaulipas, Northern Mexico, 2014-2016.

A clinical, serological, and molecular investigation was performed to determine the presence of dengue virus (DENV) and other flaviviruses among residents of the city of Reynosa, Tamaulipas, on the Mexico-U.S. border in 2014-2016. The sample population consisted of 2,355 patients with suspected dengue, in addition to 346 asymptomatic individuals recruited during a household-based epidemiological investigation designed to identify flavivirus seroconversions. Sera were collected from patients with suspected dengue in the acute phase of illness and from asymptomatic individuals at enrollment and every 5-7 months for 19 months. Sera from suspected dengue patients were tested for DENV antigen by enzyme-linked immunosorbent assay (ELISA), and select antigen-positive sera were further tested using a serotype-specific, quantitative reverse transcription-polymerase chain reaction. Sera from the household cohort were tested for flavivirus-reactive antibodies by immunoglobulin (Ig) M and IgG ELISAs using DENV antigen. A total of 418 (17.7%) patients with suspected dengue had laboratory-confirmed DENV infections, including 82 patients who were positive for DENV RNA. The most frequently detected serotype was DENV-1 (61 patients), followed by DENV-2 (16 patients) and DENV-3 (five patients). A total of 217 (62.7%) asymptomatic individuals had flavivirus-reactive antibodies at enrollment, and nine flavivirus-naïve individuals seroconverted. Sera from a subset of dengue patients and household participants, including all those who seroconverted, were further tested by plaque reduction neutralization test, resulting in the detection of antibodies to DENV-1, DENV-2, and West Nile virus. In summary, we provide evidence for the co-circulation of multiple flaviviruses in Reynosa, Tamaulipas, on the Mexico-U.S. border.