Tuesday, June 15

UA researchers develop a mathematical model to calculate the daily rate of people infected with covid-19


The number of new daily infections is one of the main parameters to understand the dynamics of an epidemic

The number of new daily infections is one of the main parameters to understand the dynamics of an epidemic

The number of daily new infections is one of the main parameters to understand the dynamics of an epidemic. However, during the covid-19 pandemic in 2020, this information has been of low quality, especially during the first months, due to the bias of the official figures due to the insufficient number of diagnostic tests performed.

Within this framework, a multidisciplinary team of researchers from the University of Alicante (UA) and Carlos III Health Institute (ISCIII) de Madrid has designed a retrospective methodology, called REMEDID (for the acronym in English of “Retrospective Methodology to Estimate Daily Infections from Deaths”), capable of estimating daily infections from the number of deaths, a figure documented with greater precision.

This work, published in the scientific journal Scientific Reports, “It helps to analyze and understand the dynamics of the pandemic and to evaluate the efficiency of the measures adopted at different spatial and temporal scales”, explains the team coordinator, the doctor in Biology and researcher at the Multidisciplinary Institute for the Study of the Environment “Ramon Margalef ”From the UA, Cesar Bordehore.

REMEDID allows calculation of time series of daily infections from time series of daily deaths. “High-fidelity time series for each parameter of an epidemic are crucial for running reliable epidemiological models. We start from the assumption that, in the first months of the pandemic, the official infection data is highly skewed downwards ”, insists Bordehore.

The red line corresponds to the official infections, and the orange to the infections estimated from the REMEDID mathematical model. The curve with the area shaded in violet are the accumulated cases of infections calculated from REMEDID, and in light blue, the accumulated cases of official infections.


Adata analysis

The team of experts has applied this precise mathematical model to estimated time series of infections, between January 8 and November 29, 2020, in Spain and its 17 communities and two autonomous cities. “The results show that the probable infections were between 35 and 42 times more than the official ones on March 14, when the government decreed the national confinement ”, points out David García, professor of the Department of Applied Mathematics of the UA and first author of the article.

According to this work, the first contagion in Spain could occur between January 8 and 9, 2020, about 43 days before the official records during the first wave. “The serology studies carried out by the Carlos III Health Institute have given us a realistic estimate of the total number of infections, showing that official data was underestimated. The REMEDID methodology complements these studies by reconstructing the temporal evolution of these infections ”, adds García.

On the other hand, they detail, “the national lockdown had an immediate effect on the transmission of the virus, as evidenced by the rapid decrease in the slope around March 14. This immediacy in the drop in transmission (the epidemiological R) was not appreciated in the official data of infected ”.

This methodology is useful for refine models and improve knowledge of the dynamics of the pandemic, including the effectiveness of the different measures taken to flatten the curve and design safe post-closure measures. “More realistic and accurate models could be obtained by using a more reliable daily number of infections provided by REMEDID, which, in turn, would improve the performance of the models and improve comparisons of different measures of slowing down transmission.” Bordehore points out.

In addition to David García and César Bordehore, this work has been developed by researchers María Isabel Vigo from the Department of Applied Mathematics of the University of Alicante; Eva S. Fonfría and Miriam Navarro from the Multidisciplinary Institute for the Study of the Environment “Ramón Margalef” of the UA, and Zaida Herrador from the Carlos III Health Institute in Madrid.


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