"For a reproductive number of 2.5 (ref. 2), contact tracing and isolation alone are less likely to be successful if more than 30% of transmission occurred befor

"For a reproductive number of 2.5 (ref. 2), contact tracing and isolation alone are less likely to be successful if more than 30% of transmission occurred before symptom onset, unless >90% of the contacts can be traced. This is more likely achievable if the definition of contacts covers 2 to 3 days prior to symptom onset of the index case, as has been done in Hong Kong and mainland China since late February. Even when the control strategy is shifting away from containment to mitigation, contact tracing would still be an important measure, such as when there are super-spreading events that may occur in high-risk settings including nursing homes or hospitals. With a substantial proportion of presymptomatic transmission, measures such as enhanced personal hygiene and social distancing for all would likely be the key instruments for community disease control." As I see it, it confirms the importance of enhanced hygiene and social distancing.