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. 2020 Oct 6;20(1):1516.
doi: 10.1186/s12889-020-09612-6.

Why crowding matters in the time of COVID-19 pandemic? - a lesson from the carnival effect on the 2017/2018 influenza epidemic in the Netherlands

LUMC-COVID-19 Research Group; Qingui Chen  1 , Myrthe M A Toorop  1 , Mark G J de Boer  2 , Frits R Rosendaal  1 , Willem M Lijfering  3
Affiliations

Why crowding matters in the time of COVID-19 pandemic? - a lesson from the carnival effect on the 2017/2018 influenza epidemic in the Netherlands

LUMC-COVID-19 Research Group et al. BMC Public Health. .

Abstract

Background: To evaluate the association between crowding and transmission of viral respiratory infectious diseases, we investigated the change in transmission patterns of influenza and COVID-19 before and after a mass gathering event (i.e., carnival) in the Netherlands.

Methods: Information on individual hospitalizations related to the 2017/2018 influenza epidemic were accessed from Statistics Netherlands. The influenza cases were stratified between non-carnival and carnival regions. Distributions of influenza cases were plotted with time and compared between regions. A similar investigation in the early outbreak of COVID-19 was also conducted using open data from the Dutch National Institute for Public Health and the Environment.

Results: Baseline characteristics between non-carnival and carnival regions were broadly similar. There were 13,836 influenza-related hospitalizations in the 2017/2018 influenza epidemic, and carnival fell about 1 week before the peak of these hospitalizations. The distributions of new influenza-related hospitalizations per 100,000 inhabitants with time between regions followed the same pattern with a surge of new cases in the carnival region about 1 week after carnival, which did not occur in the non-carnival region. The increase of new cases for COVID-19 in the carnival region exceeded that in the non-carnival region about 1 week after the first case was reported, but these results warrant caution as for COVID-19 there were no cases reported before the carnival and social measures were introduced shortly after carnival.

Conclusion: In this study, a mass gathering event (carnival) was associated with aggravating the spread of viral respiratory infectious diseases.

Keywords: COVID-19; Epidemiology; Influenza; Mass gathering medicine.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Carnival region and non-carnival region in the Netherlands. Note: The figure was created mainly using packages “cbsodataR” and “sf” with R program (R Core Team (2018). R Foundation for Statistical Computing, Vienna, Austria. Available online at https://www.R-project.org/). The geodata was retrieved via the Application Programming Interface of the Dutch National Georegistry of Public Services On the Map (PDOK) which provides a freely available access to open geo data sets of Dutch governments. Detailed R codes could be found in https://www.cbs.nl/en-gb/our-services/open-data/statline-as-open-data/cartography
Fig. 2
Fig. 2
Daily distribution of new influenza-related hospitalizations during the 2017/2018 influenza epidemic in the Netherlands
Fig. 3
Fig. 3
Daily distribution of newly diagnosed COVID-19 cases in the Netherlands
See this image and copyright information in PMC

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