On 24 February, there were nine confirmed cases of covid-19 in the UK. On the same day, the World Health Organization (WHO) recommended countries outside China with imported cases or outbreaks “prioritize active, exhaustive case finding and immediate testing and isolation, painstaking contact tracing and rigorous quarantine of close contacts.”1
On 22 March—when there were 5683 confirmed UK cases—Michael Ryan, executive director of the WHO health emergencies programme, repeated the message on the BBC: “What we really need to focus on is finding those who are sick, those who have the virus, and isolate them, find their contacts and isolate them.”
This is entirely unexceptional. Case finding, contact tracing and testing, and strict quarantine are the classic tools in public health to control infectious diseases. WHO says they have been painstakingly adopted in China, with a high percentage of identified close contacts completing medical observation. In Singapore, Vietnam, and South Korea meticulous contact tracing combined with clinical observation plus testing were vital in containing the disease.
This combined with strong measures to enforce isolation for travellers returning from high incidence areas obviated the need for a national lockdown and closure of all schools in Taiwan and Singapore.23
The mathematical model used by the UK government clearly shows that rigorous contact tracing and case finding is effective:4 the prediction of 250,000 deaths was predicated on what would happen without contact tracing.5
Contact tracing started in the UK but stopped early in the epidemic.6 How effective it was is questionable, especially in England and Wales, which made covid-19 a notifiable disease only on 5 March,78 two weeks after Scotland9 and a week after Northern Ireland.10 This, coupled with the lack of surveillance and testing of those contacting primary care, suggests the number of confirmed cases is an underestimate.
The reasons why tracing was stopped, against WHO recommendations, have not been published. It seems to be connected to a shift from “contain” to “delay” in the government’s action plan,11 when contact tracing was replaced rather than supplemented with other control measures.
One reason seems to be a lack of tests and testing facilities. However, testing is a support not a substitute for tracing or medical observation, which is crucial. Current tests for the virus require careful validation and have low sensitivity, resulting in many false negative results, especially in the pre-symptomatic phase when viral load is low. As many as 40-50% of patients tested negative initially in China, and so the definition of confirmed cases was changed to include those with clinical symptoms. …View Full Text
BMJ 2020; 368 doi: https://doi.org/10.1136/bmj.m1284 (Published 30 March 2020)Cite this as: BMJ 2020;368:m1284Read our latest coverage of the coronavirus outbreak