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Case isolation and contact tracing can contribute to the control of COVID-19 outbreaks1,2. However, it remains unclear how real-world social networks could influence the effectiveness and efficiency of such approaches. To address this issue, we simulated control strategies for SARS-CoV-2 transmission in a real-world social network generated from high-resolution GPS data that were gathered in the course of a citizen-science experiment3,4. We found that tracing the contacts of contacts reduced the size of simulated outbreaks more than tracing of only contacts, but this strategy also resulted in almost half of the local population being quarantined at a single point in time. Testing and releasing non-infectious individuals from quarantine led to increases in outbreak size, suggesting that contact tracing and quarantine might be most effective as a 'local lockdown' strategy when contact rates are high. Finally, we estimated that combining physical distancing with contact tracing could enable epidemic control while reducing the number of quarantined individuals. Our findings suggest that targeted tracing and quarantine strategies would be most efficient when combined with other control measures such as physical distancing.

A study of nearly 2,000 Marine recruits who went through supervised quarantine before starting basic training revealed several instances of asymptomatic transmission of SARS-CoV-2, the virus that causes COVID-19, despite the quarantine measures.

Actions taken to mitigate the threats of coronavirus disease 2019 (COVID-19) to human life and welfare have inadvertently resulted in a natural experiment offering unanticipated insight into how human behavior affects animal behavior (1). Worldwide, elective quarantine and stay-at-home orders have reduced use of public spaces and transportation networks, especially in cities. Anecdotal media accounts suggest that restricted movement has elicited rarely observed behaviors in commensal and peri-urban animals (2). Though not all of the reports have proven to be accurate (3), widely publicized observations like coyotes crossing the normally heavily trafficked Golden Gate Bridge in the San Francisco (SF) Bay Area (California, USA) have provoked widespread fascination with the prospect that animals rapidly move back into landscapes recently vacated by humans.

Our findings don't show much rationale for substantial relaxation of social distancing, in the absence of other measures," Wagner said. "We don't have a lot of wiggle room." Additional steps such as contact tracing, increased testing or stricter quarantining could also have an impact, he added, as will the fact that the infection rate will inevitably drop as more people contract the virus, leaving fewer susceptible.