Abstract
BackgroundThe force of infection, or the rate at which susceptible individuals become infected, is an important public health measure for assessing the extent of outbreaks and the impact of control programs.Methods and findingsWe present Bayesian methods for estimating force of infection using serological surveys of infections which produce a lasting immune response, accounting for imperfections of the test, and uncertainty in such imperfections. In this estimation, the sensitivity and specificity can either be fixed, or belief distributions of their values can be elicited to allow for uncertainty. We analyse data from two published serological studies of dengue, one in Colombo, Sri Lanka, with a single survey and one in Medellin, Colombia, with repeated surveys in the same individuals. For the Colombo study, we illustrate how the inferred force of infection increases as the sensitivity decreases, and the reverse for specificity. When 100% sensitivity and specificity are assumed, the results are very similar to those from a standard analysis with binomial regression. For the Medellin study, the elicited distribution for sensitivity had a lower mean and higher variance than the one for specificity. Consequently, taking uncertainty in sensitivity into account resulted in a wide credible interval for the force of infection.ConclusionsThese methods can make more realistic estimates of force of infection, and help inform the choice of serological tests for future serosurveys.
Highlights
The force of infection, or the rate at which susceptible individuals become infected, is an important public health measure of the speed and extent of an epidemic
International Development (DFID, www.gov.uk/ government/organisations/department-forinternational-development) under the MRC/DFID Concordat agreement, which is part of the EDCTP2 programme supported by the European Union, grant reference: MR/R010161/1, principal investigator Helen Weiss
Values of 85% sensitivity or specificity have been chosen to illustrate the method rather than on the basis of expert opinion or of comparison against a gold standard. They are in the range found for other dengue immunoglobulin G (IgG) enzyme-linked immunosorbent assay (ELISA) [37, 38]
Summary
The force of infection, or the rate at which susceptible individuals become infected, is an important public health measure of the speed and extent of an epidemic. The force of infection, or the rate at which susceptible individuals become infected, is an important public health measure for assessing the extent of outbreaks and the impact of control programs
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