COVID-19: R0 is lower where outbreak is larger

Pietro Battiston and Simona Gamba

No 438, Working Papers from University of Milano-Bicocca, Department of Economics

Abstract: We use daily data from Lombardy, the Italian region most affected by the COVID-19 outbreak, to calibrate a SIR model individually on each municipality. These are all covered by the same health system and, in the post-lockdown phase we focus on, all subject to the same social distancing regulations. We find that municipalities with a higher number of cases at the beginning of the period analyzed have a lower rate of diffusion, which cannot be imputed to herd immunity. In particular, there is a robust and strongly significant negative correlation between the estimated basic reproduction number (R0) and the initial outbreak size, in contrast with the role of R0 as a predictor of outbreak size. We explore different possible explanations for this phenomenon and conclude that a higher number of cases causes changes of behavior, such as a more strict adoption of social distancing measures among the population, that reduce the spread. This result calls for a transparent, real-time distribution of detailed epidemiological data, as such data affects the behavior of populations in areas affected by the outbreak.

Keywords: COVID-19; tests; basic reproduction number; social distancing; containment. (search for similar items in EconPapers)
JEL-codes: C22 C53 I12 I18 (search for similar items in EconPapers)
Pages: 21
Date: 2020-04, Revised 2020-04
New Economics Papers: this item is included in nep-eur, nep-hea and nep-ore
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Citations: View citations in EconPapers (9)

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Related works:
Journal Article: COVID-19: R0 is lower where outbreak is larger (2021)
Working Paper: COVID-19: $R_0$ is lower where outbreak is larger (2020)
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