A Modelling Study for Designing a Multi-layered Surveillance Approach to Detect the Potential Resurgence of SARS-CoV-2

Modelization Infectiology
Liu Y et al

Main result

In order to detect the first cases as early as possible, the testing effort should focus on "fever clinics", where suspected COVID cases are referred. Outside of hospitals, the model suggests that it is better to test younger people for early case detection, as they are less likely to have symptoms than older people, and are therefore more likely to remain undetected if not tested. 


Targeting PCR tests to suspect cases optimizes the probability of case detection.

Strength of evidence Undetermined

The article is short and the exact structure of the model is difficult to understand with the information provided.
The conclusion that testing should focus on suspected COVID cases for early detection seems logical, to the point where it is questionable whether a model was necessary. It is questionable whether there are not other more relevant aspects to optimize.


The authors divide the population into several groups: people visiting "fever clinics", hospitalised people (different services in the hospital), health care staff (in different types of services and in "fever clinics"), and the general public, and look for the best allocation of PCR tests to detect the earliest cases of SARS-CoV-2 infection.


Compartmentalized, SEAIR-type model, with age structure. The authors also assume that cured individuals may for a time continue to be PCR+. The parameters of the model are taken from the literature. The authors consider that PCR tests are perfectly specific (no false positives), and that their sensitivity varies according to whether individuals are symptomatic or not. The parameters (including the age structure) are adapted to the Beijing case.

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