Infection clusters can elevate risk of diagnostic target failure for detection of SARS-CoV-2.

The C29197T mutation is one of 4 point mutations known to cause N-gene target failure (NGTF) in the Xpert Xpress SARS-CoV-2 and Xpert Omni SARS-CoV-2 assays from Cepheid (Sunnyvale, CA). We describe a high local prevalence in January of 8.5% (CI 4.9-14.2%) for the C29197T mutation, which was over 3-fold higher than the prevalence estimated statewide in California during the same time frame, 2.5% (CI 2.1-2.8%). Using phylogenetic analysis, we discovered that this increase in prevalence was due, at least in part, to a disproportionately large infection cluster of unknown origin. This study emphasizes the importance of sequencing at the local jurisdictional level and demonstrates the impact that regional variation can have when assessing risk due to point mutations that impact clinical test performance. It also reinforces the need for diligent reporting of abnormal test results by clinical laboratories, especially during Emergency Use Authorization (EUA) periods, as additional information is gathered about the target organism and the performance of EUA-authorized tests over time.

Physical, Mental, and Financial Impacts From Drought in Two California Counties, 2015.

OBJECTIVES: To evaluate health impacts of drought during the most severe drought in California's recorded history with a rapid assessment method. METHODS: We conducted Community Assessments for Public Health Emergency Response during October through November 2015 in Tulare County and Mariposa County to evaluate household water access, acute stressors, exacerbations of chronic diseases and behavioral health issues, and financial impacts. We evaluated pairwise associations by logistic regression with pooled data. RESULTS: By assessment area, households reported not having running water (3%-12%); impacts on finances (25%-39%), property (39%-54%), health (10%-20%), and peace of mind (33%-61%); worsening of a chronic disease (16%-46%); acute stress (8%-26%); and considering moving (14%-34%). Impacts on finances or property were each associated with impacts on health and peace of mind, and acute stress. CONCLUSIONS: Drought-impacted households might perceive physical and mental health effects and might experience financial or property impacts related to the drought. Public Health Implications. Local jurisdictions should consider implementing drought assistance programs, including behavioral health, and consider rapid assessments to inform public health action.

Spatial dimensions of dengue virus transmission across interepidemic and epidemic periods in Iquitos, Peru (1999-2003).

BACKGROUND: Knowledge of spatial patterns of dengue virus (DENV) infection is important for understanding transmission dynamics and guiding effective disease prevention strategies. Because movement of infected humans and mosquito vectors plays a role in the spread and persistence of virus, spatial dimensions of transmission can range from small household foci to large community clusters. Current understanding is limited because past analyses emphasized clinically apparent illness and did not account for the potentially large proportion of inapparent infections. In this study we analyzed both clinically apparent and overall infections to determine the extent of clustering among human DENV infections. METHODOLOGY/PRINCIPAL FINDINGS: We conducted spatial analyses at global and local scales, using acute case and seroconversion data from a prospective longitudinal cohort in Iquitos, Peru, from 1999-2003. Our study began during a period of interepidemic DENV-1 and DENV-2 transmission and transitioned to epidemic DENV-3 transmission. Infection status was determined by seroconversion based on plaque neutralization testing of sequential blood samples taken at approximately six-month intervals, with date of infection assigned as the middate between paired samples. Each year was divided into three distinct seasonal periods of DENV transmission. Spatial heterogeneity was detected in baseline seroprevalence for DENV-1 and DENV-2. Cumulative DENV-3 seroprevalence calculated by trimester from 2001-2003 was spatially similar to preexisting DENV-1 and DENV-2 seroprevalence. Global clustering (case-control Ripley's K statistic) appeared at radii of ∼200-800 m. Local analyses (Kuldorf spatial scan statistic) identified eight DENV-1 and 15 DENV-3 clusters from 1999-2003. The number of seroconversions per cluster ranged from 3-34 with radii from zero (a single household) to 750 m; 65% of clusters had radii >100 m. No clustering was detected among clinically apparent infections. CONCLUSIONS/SIGNIFICANCE: Seroprevalence of previously circulating DENV serotypes can be a predictor of transmission risk for a different invading serotype and, thus, identify targets for strategically placed surveillance and intervention. Seroprevalence of a specific serotype is also important, but does not preclude other contributing factors, such as mosquito density, in determining where transmission of that virus will occur. Regardless of the epidemiological context or virus serotype, human movement appears to be an important factor in defining the spatial dimensions of DENV transmission and, thus, should be considered in the design and evaluation of surveillance and intervention strategies.

Epidemiology of dengue virus in Iquitos, Peru 1999 to 2005: interepidemic and epidemic patterns of transmission.

BACKGROUND: Comprehensive, longitudinal field studies that monitor both disease and vector populations for dengue viruses are urgently needed as a pre-requisite for developing locally adaptable prevention programs or to appropriately test and license new vaccines. METHODOLOGY AND PRINCIPAL FINDINGS: We report the results from such a study spanning 5 years in the Amazonian city of Iquitos, Peru where DENV infection was monitored serologically among approximately 2,400 members of a neighborhood-based cohort and through school-based absenteeism surveillance for active febrile illness among a subset of this cohort. At baseline, 80% of the study population had DENV antibodies, seroprevalence increased with age, and significant geographic variation was observed, with neighborhood-specific age-adjusted rates ranging from 67.1 to 89.9%. During the first 15 months, when DENV-1 and DENV-2 were co-circulating, population-based incidence rates ranged from 2-3 infections/100 person-years (p-years). The introduction of DENV-3 during the last half of 2001 was characterized by 3 distinct periods: amplification over at least 5-6 months, replacement of previously circulating serotypes, and epidemic transmission when incidence peaked at 89 infections/100 p-years. CONCLUSIONS/SIGNIFICANCE: Neighborhood-specific baseline seroprevalence rates were not predictive of geographic incidence patterns prior to the DENV-3 introduction, but were closely mirrored during the invasion of this serotype. Transmission varied geographically, with peak incidence occurring at different times among the 8 geographic zones in approximately 16 km(2) of the city. The lag from novel serotype introduction to epidemic transmission and knowledge of spatially explicit areas of elevated risk should be considered for more effective application of limited resources for dengue prevention.

Nutritional stress affects mosquito survival and vector competence for West Nile virus.

Most anautogenous female mosquitoes ingest plant carbohydrates for flight energy and survival, and they imbibe vertebrate blood for egg development. We evaluated the effect of different sucrose meals following a blood meal containing West Nile virus (WNV) on Culex pipiens pipiens survival, nutritional status, and susceptibility to viral infection and transmission. Ten days after blood feeding, no mosquitoes survived on distilled water, 55% survived on 2% sucrose, 61% on 10 and 20% sucrose meals, and over 70% survived on 40% sucrose. There was a positive correlation between sucrose meal concentration and detectable sugars, glycogen, and lipid in whole-body homogenates. Average sugar values increased from 0 microg per starved mosquito (range 0-1.0 microg) to an average of 392 microg per mosquito fed on 40% sucrose (85-1088 microg). Average glycogen values increased from 0 microg (0-5.7 microg) to an average of 620 microg (118-1421 microg). Average lipid values were identical for mosquitoes in the starved and 2% sucrose series (38 microg) and increased to 172 microg per mosquito fed on 40% sucrose (92-266 microg). Mosquitoes in all sucrose series were equally susceptible to WNV infection (p > 0.5), but mosquitoes with lower nutrient reserves as a result of lower sucrose meals were more likely to orally transmit virus (p < 0.05). We discuss how mosquito nutritional status influences probability of daily survival, susceptibility to infection, and vectorial capacity. We conclude that maintaining C. p. pipiens on standard 10% sucrose is justified in light of these results.

Mortality and reproductive dynamics of Aedes aegypti (Diptera: Culicidae) fed human blood.

Mortality is a critical factor in determining a mosquito's ability to transmit pathogens. We investigated the effect of human blood feeding and reproduction on mortality of the dengue virus vector, Aedes aegypti, by conducting a life-table study of male and female mosquitoes maintained on one of three diets: 10% sucrose, human blood or human blood plus 10% sucrose. We examined the effect of host availability by offering human blood to mosquitoes every day or every other day. Mortality of females was age-dependent and best fit by a logistic or logistic-Makeham model. The availability of blood increased survival; survival of females fed blood plus sugar was greater than those only fed sugar. There was a peak in mortality of females fed blood alone early in life that coincided with the initiation of oviposition. When females in the blood alone group were offered blood daily, their mortality was significantly lower than when they were offered blood every other day. Unlike some previous studies, females fed blood plus sugar had higher fitness than females fed blood alone. Increased fitness may have been due to differences in housing mosquitoes individually in separate cages versus as a group of many mosquitoes in each cage. It was not due to longer survival of males who had access to sugar as a food source. Our results demonstrate that reproductively active Ae. aegypti exhibit age-dependent mortality, which refutes the assumption of age-independent mosquito mortality and underscores the need to incorporate age-dependent factors into pathogen transmission models and research on mosquito biology in general.