Ronca is a postdoctoral associate at Baylor College of Medicine Houston, Texas in the Department of Pediatrics, Section of Pediatric Tropical Medicine, where she focuses researching on viral infectious diseases. Cumulative incidence of West Nile virus infection, continental United States, — Emerg Infect Dis. National Center for Biotechnology Information , U.
Journal List Emerg Infect Dis v. Shannon E. Ronca , Kristy O. Murray , and Melissa S. Author information Copyright and License information Disclaimer. Ronca, K. Murray, M. Nolan ;. Corresponding author. Address for correspondence: Kristy O. Copyright notice. This article has been cited by other articles in PMC. Associated Data Supplementary Materials Appendix Seroprevalence or cumulative incidence estimates of West Nile virus, by age, sex, and state, continental United States, — Keywords: West Nile virus, seroprevalence, United States, West Nile neuroinvasive disease, West Nile fever, asymptomatic infections, vector-borne infections, incidence, neuroinvasive disease, ArboNET, viruses, zoonoses.
Open in a separate window. Appendix: Seroprevalence or cumulative incidence estimates of West Nile virus, by age, sex, and state, continental United States, — Click here to view. Acknowledgments We would like to thank the Centers for Disease Control and Prevention staff, specifically Jennifer Lehman, for providing the data needed to calculate estimates for this study. This study was generously funded by the Chao Foundation.
References 1. Centers for Disease Control and Prevention. ArboNET [cited Feb 27]. Survival analysis, long-term outcomes, and percentage of recovery up to 8 years post-infection among the Houston West Nile virus cohort. Conversely, RRs for the untreated area versus the buffer zones alone were 0. Evaluation of efficacy is essential for assessing appropriateness of insecticide applications. However, such studies assessing the ability of adulticides to directly affect human incidence of WNV have been nonexistent.
Our findings, coupled with corroborating evidence of a reduction in the abundance of Cx. These results provide direct evidence that aerial spraying to control adult mosquitoes effectively reduced human illness and potential deaths from WNV infection. With respect to population size estimates, proportions of pretreatment cases in all treated areas and buffer zones were not different from that in the untreated area, which validates comparability of the baseline populations.
Similarly, none of the pretreatment RRs deviated from unity, which supports the assumption that treated and untreated areas had an equal likelihood, on the basis of population size, of containing a clinical case before the adulticiding, and that no preexisting factors contributed to differing disease incidence rates during that time.
These conditions are important for verifying that the untreated area was a valid comparison group for use in statistical analyses. Comparisons of buffer zones with the untreated area indicated no differences between posttreatment RR or the proportions of posttreatment cases within the 2 areas, which supports the assumption of reduced spray efficacy at the perimeter of the modeled spray cloud. This finding may have implications for future aerial applications and efficacy studies.
Additionally, posttreatment infiltration of Cx. On the basis of mean dispersal distances of Cx. However, results of all statistical tests remained unchanged after combining the number of cases from buffer zones and treated areas, and these posttreatment reductions of cases still differed from that in the untreated area Table 2. Because posttreatment proportions of cases were lower than in the untreated area, we rejected the null hypothesis of goodness-of-fit comparisons.
Our results also indicate that there were associations between adulticiding and temporal classification of cases. Therefore, we also rejected the null hypothesis of tests of independence. Without applications of aerial adulticide, more Sacramento residents would have been infected with WNV. Although there was a negative correlation between aerial treatments and incidence of human cases, causation is predicated upon spraying having a direct effect on mosquito populations.
Recent work showed that adulticiding immediately reduced abundance and infection rates of Culex spp. Using factorial 2-way analysis of variance, these researchers compared mean abundances of Cx. Abundance of Cx. Regardless, we reason that Cx. A Elnaiem, unpub. Pools of mosquitoes were tested for WNV by using a reverse transcription—PCR, and infection rates were calculated by using a bias-corrected maximum likelihood estimation www. After spraying, infection rates decreased from 8.
Furthermore, no additional positive pools were detected in the northern treatment area during the remainder of the year, whereas positive pools were detected in the untreated area until the end of September D.
These findings are consistent with others from Sacramento County in , which indicated that mosquito infection rates peaked in July and August Considering early summer amplification within vector populations and length of the human incubation period, WNV remediation efforts would be more effective in limiting illness and death associated with human infection if conducted at the onset of enzootic amplification rather than after occurrence of human cases.
He is currently pursuing master of public health and master of business administration degrees at Yale University. His research interests include surveillance and epidemiology of zoonotic and vector-borne diseases, geographic information systems and spatial modeling, and evolution of avian flight.
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Figure 1 Figure 2 Figure 3 Figure 4. Table 1 Table 2. Article Metrics. Related Articles. Abstract Epidemic transmission of West Nile virus WNV in Sacramento County, California, in prompted aerial application of pyrethrin, a mosquito adulticide, over a large urban area. Adulticide Application Figure 1 Figure 1. Assumptions As is standard practice in most epidemiologic studies, residential addresses of patients were assumed to be locations of disease transmission; this is also consistent with other WNV studies 25 — Figure 2 Figure 2.
Figure 3 Figure 3. Figure 4 Figure 4. Virology, pathology, and clinical manifestations of West Nile virus disease. Emerg Infect Dis. PubMed Google Scholar. California Department of Health Services. Vector-Borne Disease Section. Vector-borne diseases in California, : annual report. Updated Feb 9. Updated Mar Centers for Disease Control and Prevention. West Nile virus activity in the United States. Updated Feb Atlanta: The Centers; [cited Apr 11].
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