Abstract
On 31 December, 2019, an outbreak of a novel coronavirus, SARS-CoV-2, that causes the COVID-19 disease, was first reported in Hubei, mainland China. This epidemics’ health threat is probably one of the biggest challenges faced by our interconnected modern societies. According to the epidemiological reports, the large basic reproduction number , together with a huge fraction of asymptomatic infections, paved the way for a major crisis of the national health capacity systems. Here, we develop an age-stratified mobility-based metapopulation model that encapsulates the main particularities of the spreading of COVID-19 regarding (i) its transmission among individuals, (ii) the specificities of certain demographic groups with respect to the impact of COVID-19, and (iii) the human mobility patterns inside and among regions. The full dynamics of the epidemic is formalized in terms of a microscopic Markov chain approach that incorporates the former elements and the possibility of implementing containment measures based on social distancing and confinement. With this model, we study the evolution of the effective reproduction number , the key epidemiological parameter to track the evolution of the transmissibility and the effects of containment measures, as it quantifies the number of secondary infections generated by an infected individual. The suppression of the epidemic is directly related to this value and is attained when . We find an analytical expression connecting with nonpharmacological interventions, and its phase diagram is presented. We apply this model at the municipality level in Spain, successfully forecasting the observed incidence and the number of fatalities in the country at each of its regions. The expression for should assist policymakers to evaluate the epidemics’ response to actions, such as enforcing or relaxing confinement and social distancing.
- Received 11 August 2020
- Revised 1 October 2020
- Accepted 12 November 2020
DOI:https://doi.org/10.1103/PhysRevX.10.041055
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
The spread of COVID-19 is posing an unprecedented threat to health systems worldwide. The fast propagation of the disease combined with the existence of covert contagions by asymptomatic individuals make controlling this disease particularly challenging. Here, we develop a tailored model for the epidemic spreading of COVID-19 that encapsulates many of the peculiarities of this disease, allowing us to describe how containment measures impact the transmission of the virus.
The key parameter to track the progression of the epidemic is the effective reproduction number , defined as the number of secondary infections generated by an infected individual. The suppression of the epidemic is directly related to this value and is attained when .
Our model provides an analytical expression for as a function of mobility restrictions and confinement measures, taking into account transmission among individuals, impact of COVID-19 on certain demographic groups, and the movement of individuals within and among various regions. This expression for is an extremely useful tool to design containment policies that are able to suppress the epidemic.
We apply our epidemic model for the case of Spain, successfully forecasting both the observed incidence in each region and the overload of the health system. The expression we derive for allows policy makers to determine the precise reduction of mobility and degree of confinement needed to bend the curve of epidemic incidence.
