Incubation period of typhoidal salmonellosis : a systematic review and meta-analysis of outbreaks and experimental studies occurring over the last century

Background Salmonella Typhi is a human pathogen that causes typhoid fever. It is a major cause of morbidity and mortality in developing countries and is responsible for several outbreaks in developed countries. Studying certain parameters of the pathogen, such as the incubation period, provides a better understanding of its pathophysiology and its characteristics within a population. Outbreak investigations and human experimental studies provide an avenue to study these relevant parameters. Methods In this study, the authors have undertaken a systematic review of outbreak investigation reports and experimental studies, extracted reported data, tested for heterogeneity, identified subgroups of studies with limited evidence of heterogeneity between them and identified factors that may contribute to the distribution of incubation period. Following identification of relevant studies, we extracted both raw and summary incubation data. We tested for heterogeneity by deriving the value of I2 and conducting a KS-test to compare the distribution between studies. We performed a linear regression analysis to identify the factors associated with incubation period and using the resulting p-values from the KS-test, we conducted a hierarchical cluster analysis to classify studies with limited evidence of heterogeneity into subgroups. Results We identified thirteen studies to be included in the review and extracted raw incubation period data from eleven. The value of I2 was 84% and the proportion of KS test p-values that were less than 0.05 was 63.6% indicating high heterogeneity not due to chance. We identified vaccine history and attack rates as factors that may be associated with incubation period, although these were not significant in the multivariable analysis (p-value: 0.1). From the hierarchical clustering analysis, we classified the studies into five subgroups. The mean incubation period of the subgroups ranged from 9.7 days to 21.2 days. Outbreaks reporting cases with previous vaccination history were clustered in a single subgroup and reported the longest incubation period. Conclusions We identified attack rate and previous vaccination as possible associating factors, however further work involving analyses of individual patient data and developing mathematical models is needed to confirm these as well as examine additional factors that have not been included in our study

Bacteriological evaluation of some sachet water on sales in Owerri metropolis, Imo State, Nigeria

Aims: Continuous increase in the sale and indiscriminate consumption of packaged drinking waters in Nigeria is of public health significance. In order to safe guard public health, it is essential that the available packaged water is of the highest quality. This study was carried out to evaluate the bacteriological quality of packaged water on sale in Owerri metropolis, Imo State of Nigeria.Methodology and Results: From 30 registered sachet water factories, 8 samples each was purchased randomly fifteen of the brands of sachet water all over Owerri metropolis in Imo State, Southeastern Nigeria. These were analyzed for presence of bacterial indicators of water quality. Four weeks later, a second batch of the samples was collected from other brands. A mean plate counts was taken and the organisms from each water sample identified using standard procedures. The results showed that 11 (73.3%) sachet water brands had growths of pathogenic organisms in the first batch while 10 (66.6%) had growth in the second batch. The isolates were identified to be Klebsilla spp., Serratia spp., Proteus spp., Pseudomonas aeruginosa and Chromobacterium spp. The study showed that Klebsiella pneumoniae [7(29.2%)] was the most predominant. This was closely followed by Serratia spp. [6(25.0%)] and Proteus mirabilis [6(25.0%)]. Pseudomonas aeruginosa [3(12.5%)] and Chromobacterium spp. [2(8.3%)] was least predominant. Mean total heterotrophic bacteria plate counts (HPC) per millilitre ranged from 0.0 to 6.0 x 102 CFU/mL at 22 °C and 0.0 to 7.0 x 102 CFU/mL at 37 °C (first batch) and 0.0 to 5.0 x 102 CFU/mL at 22 °C and 0.0 to 10.0 x 102 CFU/mL at 37 °C for the second batch. Thus they fell below the United States Environmental Protection Agency (USEPA) and World Health Organization (WHO) drinking water standard of 100 HPC per millilitre of water. Bacteriological examination of different brands of sachet water samples collected from different locations showed that only Vince water and Akudo table water was found to be safe for drinking while the other brands of sachet water from mobile vendors in Owerri metropolis was not potable.Conclusion, Significance and Impact of study: Hence, the bacteriological quality of some of the brands of sachet water on sale in Owerri was of poor quality index. The study suggests that sachet water could be a route of transmission of enteric pathogens among the populace. In order to safe guard public health, highest quality brands of sachet water is therefore advocated

From curiosity to commodity: a review of the evolution of sachet drinking water in West Africa

The private sector continues to play an important role in filling local drinking water supply gaps across the Global South. In West Africa, a perfect storm of rapid population growth, infrastructure mismanagement, and globalization of consumer markets has resulted in the advent of an entire new industry around packaged water, primarily ‘sachet water’ sold in mechanically sealed plastic sleeves. Most local governments and international development agencies have historically perceived sachet water as a passing trend, but it has quickly become a primary drinking water source for the majority of households in many urban areas and continues to spread throughout the region and world. Sachet water is now an important component of regional water security, although with attendant issues related to governance, quality control, environmental pollution, and social justice. This paper reviews the seminal literature on sachet water in West Africa, with particular emphasis on Ghana and Nigeria, where most studies have focused. This review synthesizes governance issues, consumer and industry trends, and the latest on product quality in the literature from 2011 to 2016, with 2010 approximating an inflection point for the modernization of the industry. The ability of many West African nations to achieve universal access to safe drinking water may depend on their willingness to understand and incorporate the sachet water industry into an integrated drinking water platform. WIREs Water 2017, 4:e1206. doi: 10.1002/wat2.1206 This article is categorized under: Engineering Water > Planning Water Engineering Water > Sustainable Engineering of Water Human Water > Water Governance A typical 500‐mL sachet of drinking water sold in Accra, Ghana