Optimal Sampling Strategies for Detecting Zoonotic Disease Epidemics

Abstract

The early detection of disease epidemics reduces the chance of successful introductions into new locales, minimizes the number of infections, and reduces the financial impact. We develop a framework to determine the optimal sampling strategy for disease detection in zoonotic host-vector epidemiological systems when a disease goes from below detectable levels to an epidemic. We find that if the time of disease introduction is known then the optimal sampling strategy can switch abruptly between sampling only from the vector population to sampling only from the host population. We also construct time-independent optimal sampling strategies when conducting periodic sampling that can involve sampling both the host and the vector populations simultaneously. Both time-dependent and -independent solutions can be useful for sampling design, depending on whether the time of introduction of the disease is known or not. We illustrate the approach with West Nile virus, a globally-spreading zoonotic arbovirus. Though our analytical results are based on a linearization of the dynamical systems, the sampling rules appear robust over a wide range of parameter space when compared to nonlinear simulation models. Our results suggest some simple rules that can be used by practitioners when developing surveillance programs. These rules require knowledge of transition rates between epidemiological compartments, which population was initially infected, and of the cost per sample for serological tests.

Using spatial tools for high impact zoonotic agents’ surveillance design in backyard production systems from central Chile

“…21 Delays in field activities could affect the integrity of the sample, depending on the type of the sample and the agent involved. 22,23 Previous work in our research group spent almost one day just to reach one allocated random point and then search for the closest BPS to sample (Di Pillo, F. data not published). According to the characteristics of these production systems, most birds or pigs are raised in partially enclosed systems, where animals are confined at night and released to an extensive rearing during the day, increasing the difficulty of sampling.…”

A method of determining where to target surveillance efforts in heterogeneous epidemiological systems

“…The concept of surveillance within a host-vector system has been previously studied by Ferguson and others [ 65 ], who found that the relative prevalences and the costs of sampling determined the probability of detection in any group at any single sampling point. This shares similarities with our own formulation, since the ratio can be considered the ratio of prevalences amongst hosts and vectors during initial exponential growth.…”

“…This shares similarities with our own formulation, since the ratio can be considered the ratio of prevalences amongst hosts and vectors during initial exponential growth. As with our approach, the Ferguson model had threshold-like behaviour in which the optimal sampling strategy suddenly changed, with the optimal sampling strategy generally being to focus on a single group of interest [ 65 ].…”

Probing Complexity with Epidemics: A New Reactive Immunization Strategy

“…First, our scheme, so as many other standard immunization strategies, is strongly information-demanding. Of course, a full knowledge about the complex system is rather unlikely in real situations, then sampling and interpolation (Ferguson et al, 2014), so as data assimilative strategies (Rhodes and Hollingsworth, 2009) have been recently developed. The second aspect concerns the role of the tunable parameters in our strategy.…”