key: cord-267494-186aztc3
authors: Wilder-Smith, Annelies; Bar-Yam, Yaneer; Fisher, Dale
title: Lockdown to contain COVID-19 is a window of opportunity to prevent the second wave
date: 2020-05-30
journal: J Travel Med
DOI: 10.1093/jtm/taaa091
sha: 
doc_id: 267494
cord_uid: 186aztc3

nan

We know what can happen when COVID-19 catches a city off guard. Wuhan, central China, the unsuspecting ground zero of the COVID-19 outbreak, saw a tsunami of tens of thousands of COVID-19 cases quickly overwhelm their health care system within a matter of weeks. After some initial delays -now typical for many other countries -China reacted swiftly and relentlessly. China escalated a response unlike any the world has seen before and which many have still not fully appreciated. Extraordinary public health measures, pulling from the full armamentarium of non-pharmaceutical interventions 1 , were implemented. These included early identification of cases by prompt laboratory testing, hospital or facility-based isolation of all cases 2 , rigorous contact tracing and meticulous follow-up of quarantined contacts, enhanced by artificial intelligence. 3 In the community, mobility was restricted and social contact minimised.

A lockdown of the entire city was instituted to protect the rest of the country and the rest of the world. The lockdown started on 23 January, 2020, at a time of 495 laboratory confirmed cases. New cases continued to increase exponentially before peaking on 12 Policy-makers are debating two strategies to reduce deaths and the demand on health care utilization 6 , in addition to considering major collateral damage to economic, society, mental health and other outcomes: (a) containment or suppression of COVID-19, which aims to reverse the rate of epidemic growth, thereby reducing new case numbers to low levels, and (b) mitigation, which focuses on slowing but not necessarily stopping epidemic spread -to reduce peak healthcare demand while protecting those most at risk of severe disease from infection. Containment requires all out action to reduce the reproductive number, R, to below 1, thus causing case numbers to decline. Mitigation aims to merely slow spread by reducing R, but not to below 1, and new cases continue to rise.

There are three reasons why containment is the much-preferred option. First, the rapid reduction in the number of cases that can be achieved is almost the mirror of the rapid increase, occurring over a very short period of time-potentially as short as a few weeks.

Second, the period of large-scale impacts including suffering, death and economic impacts is limited to these weeks. Third, an all-out short-term approach to containment will most likely have a lower socio-economic impact than longer-term mitigation efforts. Second, active case finding and reporting: The benefit of rapid laboratory testing of even mildly symptomatic cases with prompt isolation, and contact tracing with enforced quarantine of contacts should be clear. 8 The delay between symptom onset and isolation has the largest role in determining whether an outbreak would be controllable, therefore

prompt isolation of all cases should be the primary goal. 9 Cases that are not isolated result in a high secondary attack rate. Institution-based isolation, even of mild cases, was modelled to reduce the outbreak size by more than 50%. 10 outbreaks. Modelling has shown that not all contacts need to be identified to ensure a suppression of the epidemic curve. Across different initial numbers of cases, the majority of scenarios with an R 0 of 1.5 were controllable with less than 50% of contacts successfully

traced, and to control the majority of outbreaks, for R 0 of 2.5 more than 70% of contacts have to be traced. 9 The lockdown is a window of opportunity to bolster basic public health systems. Lockdowns are being eased incrementally in many locations. Unfortunately, many countries are relaxing restrictions without having achieved zero community transmission, without which a resurgence is likely both increasing incidence of disease and prolonging the time until full reopening is possible. All countries are naturally keen to restart their economies but priorities also factor in social and cultural activities of importance. Arrangements for air travel between specific countries are underway and risks are high unless both countries are near or at zero transmission.

While testing and contact tracing capacity have been ramped up, these are only effective when the number of cases is small enough. While some individuals, communities and countries are continuing to take social distancing seriously, the enthusiasm about returning to normalcy has the potential to undermine the lessons learnt. It seems many have forgotten how aggressive this virus is in death, in severity of disease, and in crippling a health system, overwhelming it and allowing amplification of fatalities. More cases and more clusters will appear and different countries will manage these differently. Indeed, it is likely that as countries come out of lockdown most will need to revisit lockdowns in some form or another as community transmission grows. How this is managed will be a major test of leadership and community engagement in every country. The opportunity remains to use widespread testing to selectively identify regions of a country and reopen economic activity and travel as those regions become transmission free, accelerating the process of economic recovery. 

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