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Multiple exposures, reinfection and risk of progression to active tuberculosis.

ABSTRACT: A recent study reported on a tuberculosis (TB) outbreak in a largely Inuit village. Among newly infected individuals, exposure to additional active cases was associated with an increasing probability of developing active disease within a year. Using binomial risk models, we evaluated two potential mechanisms by which multiple infections during the first year following initial infection could account for increasing disease risk with increasing exposures. In the reinfection model, each infectious contact confers an independent risk of an infection, and infections contribute independently to active disease. In the threshold model, disease risk follows a sigmoidal function with small numbers of infectious contacts conferring a low risk of active disease and large numbers of contacts conferring a high risk. To determine the dynamic impact of reinfection during the early phase of infection, we performed simulations from a modified Reed-Frost model of TB dynamics following spread from an initial number of cases. We parametrized this model with the maximum-likelihood estimates from the reinfection and threshold models in addition to the observed distribution of exposures among new infections. We find that both models can plausibly account for the observed increase in disease risk with increasing infectious contacts, but the threshold model confers a better fit than a nested model without a threshold (p = 0.04). Our simulations indicate that multiple exposures to infectious individuals during this critical time period can lead to dramatic increases in outbreak size. In order to decrease TB burden in high-prevalence settings, it may be necessary to implement measures aimed at preventing repeated exposures, in addition to preventing primary infection.

SUBMITTER: Ackley SF

PROVIDER: S-EPMC6458392 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature

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Multiple exposures, reinfection and risk of progression to active tuberculosis.

Ackley Sarah F SF Lee Robyn S RS Worden Lee L Zwick Erin E Porco Travis C TC Behr Marcel A MA Pepperell Caitlin S CS

Royal Society open science 20190320 3

A recent study reported on a tuberculosis (TB) outbreak in a largely Inuit village. Among newly infected individuals, exposure to additional active cases was associated with an increasing probability of developing active disease within a year. Using binomial risk models, we evaluated two potential mechanisms by which multiple infections during the first year following initial infection could account for increasing disease risk with increasing exposures. In the <i>reinfection model</i>, each infe ...[more]

PMID: 31031990

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Project description:BackgroundMultiple sclerosis (MS) is the most common non-traumatic condition that leads to disability among young individuals. It is associated with demyelination, inflammation, and neurodegeneration within the central nervous system. Information on risk factors of multiple sclerosis is crucial for the prevention and control of the disease. The aim of this study was to determine risk factors of MS among adults in Saudi Arabia.MethodsA matched multicenter case-control study, including 307 MS patients and 307 healthy controls, was conducted in MS clinics and wards in 3 main cities of Saudi Arabia. Age, gender, and hospital were matched. Information on demographics, family history of MS, past medical and family history, sun exposure at different age periods, tobacco use, diet, consanguinity, and coffee consumption was obtained from self-administered questionnaires. ORs and 95% confidence intervals (CIs) were calculated. A conditional logistic regression model was used to control for potential confounding factors.ResultsThe conditional logistic regression adjusted for age and gender showed that being the first child in the family (Adjusted Odds Ratio (AOR) 1.68, 95% CI: 1.03-2.74), having a family history of MS (AOR 5.83, 95% CI: 2.83-12), eating fast food ≥5 times weekly (AOR 2.05, 95% CI: 1.03-4.08), and having had measles (AOR 3.77, 95% CI: 2.05-6.96), were independently associated with an increased risk of MS. In contrast, eating ≥5 servings of fruit per week (AOR 0.25, 95% CI: 0.16-0.38), drinking coffee daily (AOR 0.46, 95% CI: 0.31-0.68), and having a high level of sun exposure at the primary school level and university level (AOR 0.57, 95% CI: 0.38-0.85 and AOR 0.48, 95% CI: 0.30-0.76, respectively) were independently associated with a decreased risk of MS.ConclusionsOur study suggested that high levels of sun exposure during primary school and university, consumption of fruits and drinking coffee protect against MS. In contrast, eating fast food was associated with an increased risk of the disease. Encouraging outdoor activity and healthy diets in school, especially for females, is highly recommended.

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Multiple exposures, reinfection and risk of progression to active tuberculosis.

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Multiple exposures, reinfection and risk of progression to active tuberculosis.

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