Kathryn Morrison

Reconstruction of Zika Virus Introduction in Brazil.

We estimated the speed of Zika virus introduction in Brazil by using confirmed cases at the municipal level. Our models indicate a southward pattern of introduction starting from the northeastern coast and a pattern of movement toward the western border with an average speed of spread of 42 km/day or 15,367 km/year.

Effectiveness of monovalent rotavirus vaccine in a high-income, predominant-use setting.

BACKGROUND AND OBJECTIVES We assessed monovalent rotavirus (RV1) vaccine effectiveness (VE) in a high-income setting with RV1 predominant use, and examined the burden of pediatric rotavirus gastroenteritis following the implementation of an RV1-only vaccination program. METHODS We conducted active rotavirus gastroenteritis surveillance among children 8 weeks to <3 years of age at three hospitals. Participant information and vaccination histories were collected via parent/guardian interview and medical records. Stool specimens were tested for rotavirus; positive specimens were genotyped. The effect of increasing RV1 coverage on rotavirus prevalence was examined as a weekly time series via binomial regression with a log link function, using either categorical season or mean 2-dose rotavirus seasonal vaccine coverage as the exposure variable. As compared with RV1 vaccine formulation, rotavirus genotypes were classified as homotypic, partly-heterotypic, or heterotypic; prevalence of each was compared by season. A test-negative case-control design was used to examine RV1 VE against hospitalization or emergency visits. RESULTS We enrolled 866 participants in active surveillance; of these, 384 (44.3%) were eligible for VE analyses. After adjustment for season, we detected a 70.1% (95% CI: 21.9%, 88.6%) relative decrease in rotavirus prevalence in the 2013-14 season compared with 2012-13 season. On average, a 1% increase in ≥2-dose rotavirus coverage among children 1 year of age was associated with a 3.8% (95% CI: 1.8%, 5.8%) relative decrease in rotavirus prevalence. Rotavirus homotypic strain prevalence decreased, with 77% (95% CI: 68%, 89%) versus 8% (95% CI: 0%, 36%) prevalence during the 2011-12 and 2013-14 seasons, respectively. Adjusted 2-dose RV1 VE was 91.2% (95% CI: 61.6%, 98.0%). CONCLUSIONS RV1 vaccine was highly effective to prevent rotavirus hospitalizations and emergency visits among children <3 years of age in a high-income setting with its predominant use. Our estimates were similar to high-income settings with concurrent RV1 and pentavalent vaccine use.

The velocity of Ebola spread in parts of west Africa

www.thelancet.com/infection Vol 15 September 2015 1005 1 Gao L, Lu W, Bai L, et al, for the LATENTTB-NSTM study team. Latent tuberculosis infection in rural China: baseline results of a population-based, multicentre, prospective cohort study. Lancet Infect Dis 2015; 15: 310–19. 2 Farhat M, Greenaway C, Pai M, Menzies D. False-positive tuberculin skin tests: what is the absolute eff ect of BCG and nontuberculous mycobacteria? Int J Tuberc Lung Dis 2006; 10: 1192–204. 3 Jing H, Wang H, Wang Y, et al. Prevalence of nontuberculous mycobacteria infection, China, 2004–2009. Emerg Infect Dis 2012; 18: 527–28. 4 Menzies D. What does tuberculin reactivity after bacille Calmette-Guerin vaccination tell us? Clin Infect Dis 2000; 31 (suppl 3): S71–S74. 5 Wang L, Liu J, Chin DP. Progress in tuberculosis control and the evolving publichealth system in China. Lancet 2007; 369: 691–96.

A latent process model for forecasting multiple time series in environmental public health surveillance

This paper outlines a latent process model for forecasting multiple health outcomes arising from a common environmental exposure. Traditionally, surveillance models in environmental health do not link health outcome measures, such as morbidity or mortality counts, to measures of exposure, such as air pollution. Moreover, different measures of health outcomes are treated as independent, while it is known that they are correlated with one another over time as they arise in part from a common underlying exposure. We propose modelling an environmental exposure as a latent process, and we describe the implementation of such a model within a hierarchical Bayesian framework and its efficient computation using integrated nested Laplace approximations. Through a simulation study, we compare distinct univariate models for each health outcome with a bivariate approach. The bivariate model outperforms the univariate models in bias and coverage of parameter estimation, in forecast accuracy and in computational efficiency. The methods are illustrated with a case study using healthcare utilization and air pollution data from British Columbia, Canada, 2003-2011, where seasonal wildfires produce high levels of air pollution, significantly impacting population health. Copyright

The impact of geographical location of residence on disease outcomes among Canadian First Nations populations during the 2009 influenza A(H1N1) pandemic

We sought to evaluate the effect of geographical location of residence on disease burden in Canadian First Nations (FN) populations during the 2009 pandemic influenza A(H1N1). Descriptive statistics and regression analysis of data for cases of pandemic A(H1N1) infection and hospitalization in the province of Manitoba, Canada, were conducted to estimate the odds of hospitalization and delay in time-to-hospitalization for on-reserve and off-reserve FN populations, while considering their geographical proximity to urban centers. We found that on-reserve FN individuals experienced a longer delay between infection and hospitalization compared to off-reserve FN individuals (p<0.001). The average fraction of FN cases that experienced a delay longer than 4 days for hospitalization was 20% higher for on-reserve compared to off-reserve residence. The odds of hospitalization were twice as high for FN people living on-reserve as compared to off-reserve (odds ratio=2.34; 95% CI: 1.16-4.73). Given the independent effect of on-reserve residency, higher disease burden among FN people cannot be attributed entirely to limited healthcare access due to remoteness from urban centers.

Spatial Determinants of Ebola Virus Disease Risk for the West African Epidemic

Introduction: Although many studies have investigated the probability of Ebola virus disease (EVD) outbreaks while other studies have simulated the size and speed of EVD outbreaks, few have investigated the environmental and population-level predictors of Ebola transmission once an outbreak is underway. Identifying strong predictors of transmission could help guide and target limited public health resources during an EVD outbreak. We examined several environmental and population-level demographic predictors of EVD risk from the West African epidemic. Methods: We obtained district-level estimates from the World Health Organization EVD case data, demographic indicators obtained from the Demographic and Health surveys, and satellite-derived temperature, rainfall, and land cover estimates. A Bayesian hierarchical Poisson model was used to estimate EVD risk and to evaluate the spatial variability explained by the selected predictors. Results: We found that districts had greater risk of EVD with increasing proportion of households not possessing a radio (RR 2.79, 0.90-8.78; RR 4.23, 1.16-15.93), increasing rainfall (RR 2.18; 0.66-7.20; 5.34, 1.20-23.90), and urban land cover (RR 4.87, 1.56-15.40; RR 5.74, 1.68-19.67). Discussion: The finding of radio ownership and reduced EVD transmission risk suggests that the use of radio messaging for control and prevention purposes may have been crucial in reducing the EVD transmission risk in certain districts, although this association requires further study. Future research should examine the etiologic relationships between the identified risk factors and human-to-human transmission of EVD with a focus on factors related to population mobility and healthcare accessibility, which are critical features of epidemic propagation and control.

Two Birds with One Stone: Estimating Population Vaccination Coverage from a Test-Negative Vaccine Effectiveness Case-Control Study

Vaccination program evaluation includes assessment of vaccine uptake and direct vaccine effectiveness (VE). Often examined separately, we propose a design to estimate rotavirus vaccination coverage using controls from a rotavirus VE test-negative case-control study and to examine coverage following implementation of the Quebec, Canada, rotavirus vaccination program. We present our assumptions for using these data as a proxy for coverage in the general population, explore effects of diagnostic accuracy on coverage estimates via simulations, and validate estimates with an external source. We found 79.0% (95% confidence interval, 74.3%, 83.0%) ≥2-dose rotavirus coverage among participants eligible for publicly funded vaccination. No differences were detected between study and external coverage estimates. Simulations revealed minimal bias in estimates with high diagnostic sensitivity and specificity. We conclude that controls from a VE case-control study may be a valuable resource of coverage information when reasonable assumptions can be made for estimate generalizability; high rotavirus coverage demonstrates success of the Quebec program.

Trends in the contribution of major causes of death to the black-white life expectancy gap by US state

&NA; Life expectancy has increased in the United States over many decades. The difference in life expectancy between black and white Americans has also decreased, but some states have made much more progress towards racial equality than others. This paper describes the pattern of contributions of six major causes of death to the black‐white life expectancy gap within US states and the District of Columbia between 1969 and 2013, and identifies states diverging from the overall pattern. Across multiple causes, the District of Columbia, Illinois, Wisconsin, and Michigan had the highest contributions to black‐white inequality, while New York, Massachusetts, and Rhode Island had the lowest contributions and have either achieved or are the closest to achieving black‐white equality in life expectancy.