key: cord-0711958-z88fgbsr
authors: Kwok, Kin On; Lai, Florence; Wei, Vivian Wan In; Tsoi, Margaret Ting Fong; Wong, Samuel Yeung Shan; Tang, Julian
title: Comparing the impact of various interventions to control the spread of COVID-19 in 12 countries
date: 2020-06-30
journal: J Hosp Infect
DOI: 10.1016/j.jhin.2020.06.029
sha: 33e4cea29904c16274f7f53697fac7713f3efc60
doc_id: 711958
cord_uid: z88fgbsr

nan

Since the start of the coronavirus disease 2019 (COVID-19) pandemic (caused by severe acute respiratory syndrome coronavirus 2, SARS-CoV-2) [1], multiple countries have implemented various interventions to reduce the disease introduction into their populations. These have included border closure, travel restrictions and compulsory quarantine for foreigners entering these countries [2, 3] .

Additional interventions to reduce the local spread of the virus have included the wearing of surgical masks, mass-testing for SARS-CoV-2, travel restrictions, the banning of mass gatherings (of various sizes); the closure of mosques, bars and restaurants, schools and universities; curfews and stay-at-home orders, and the stoppage of all 'non-essential' work [2, 3] .

Here we examine the impact of these interventions across 12 countries with the most complete data available from either media or government websites: the United States (US), Canada, the United Kingdom (UK), France, Germany, Italy, Denmark, India, Thailand, Malaysia, Singapore and Australia.

For each country, the daily number of COVID-19 cases was extracted [4] and plotted over time, along with the number of diagnostic tests or people tested for SARS-CoV-2 performed [5], population wearing masks proportion (%masking) [6] , and the degree of travel restriction by examining the change in volume of people walking in their communities to provide a countrybased mobility trend ('mobility index') [7] . Next, we indicated the dates where individual or combined intervention was implemented [8] , and plotted the estimated daily effective reproductive number, Rt [9] -an average number of secondary cases generated by a typical case at time t under the control measures in place, with 90% confidence intervals (90% CI) plotted on the same timeline ( Fig. 1) . Rt is a useful measure to evaluate the effectiveness of public health interventions at a regular interval. In the country examples shown (Italy - Fig. 1A and UK -Fig. 1B) , the Rt values have decreased to 1 or below, from a previously higher value of around 2, which may be attributed to the interventions that were implemented. While these two study populations become more mobilized after lockdown easing, Rt remains slightly smaller than 1 with improving testing capacity.

From each of the countries' plots, we can observe several trends: i) the testing pattern follows the daily number of new COVID-19 cases, which is not unexpected -you will only identify more cases by testing; ii) similarly, the %masking also follows the number of cases (or Rt) ( Fig.  S1A to Fig. S1M )-which may be a likely population response to the increasing numbers of cases, where sufficient masks are available; iii) the mobility index and Rt are strongly correlated -this is reasonable as Rt will depend on the number of contacts with susceptibles, and this will be reduced if mobility is reduced when the social interventons are in place (Fig. S2A to Fig. S2M) , though the relationship of both these parameters with the number of cases is unclear; iv) any decrease in the number of cases due to any intervention (Table S1 ) tends to be seen 2-4 weeks later but this is not consistent and seems not to depend on the country's population size. For example, Australia (Fig S3K) , Italy (Fig. 1A) , Germany (Fig. S3D ) appear to show a decrease in the number of daily COVID-19 cases approximately 2 weeks after their first intervention, i.e. a 14-day quarantine imposed in Australia, a 'lockdown in Italy, where citizens had to stay at home except for essential needs, and the closure of mosques in Germany. The Rts for these three countries are currently below 1 (at the time of analysis), though that for Australia appears to be drifting upwards. US (Fig. S3A) , India (Fig. S3F) , Singapore (Fig. S3H) show similar patterns of daily new cases in the early phase despite their massively different population sizes, with US first banning public events and state-wide stay-at-home order in majority of states, India first closing restaurants and Singapore first imposing a 14-day quarantine for all foreign visitors. India has not yet reached its peak of cases, though its Rt values are decreasing towards 1 (at the time of analysis). Number of cases in Singapore and US are now both decreasing with Rt about 1. No single intervention was observed to produce a definitive and immediate reduction in the number of daily COVID-19 cases.

For the other countries, Rt values of Canada (Fig. S3B) , France (Fig. S3C) , Denmark (Fig.  S3E) , Malaysia (Fig. S3G) and Thailand (Fig. S3J) have reached or dropped below 1, though worryingly (at the time of analysis), some are showing some recent signs of rising beyond this threshold again (France, Denmark, Malaysia, Thailand) -which may be due to a fluctuating degree of compliance with the interventions in a proportion of these populations or ease of lockdown.

Despite the data uncertainty, the different intervention combinations implemented within each country, and a variable level compliance with them within each population, we have observed some useful and encourging trends in the multi-country COVID-19 data presented here. Country or territory specific modelling study should be conducted individually to quantify the impact of single or bundled measures on COVID-19 activity and what level of lockdown easing would trigger another phase of epidemic. 

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COVID-19 situation in the WHO European Region World Health Organization

Centres for Disease Control and prevention (CDC)

Guidance on social distancing for everyone in the UK

European Centre for Disease Prevention and Control

Coronavirus Pandemic (COVID-19). Our World in Data 2020

International COVID-19 tracker update: 18 May | YouGov

Estimating the number of infections and the impact of non-pharmaceutical interventions on COVID-19 in 11 European

Singapore School closure ordered National-wide school closure 8/4/2020

The first policy implementation date in cities/states in the US.