The study says that substantial proportion of transmission probably occurs even before first symptoms appear in the infected person. Since most cases were isolated soon after they showed symptoms, the possibility of virus spread after symptoms showed up was prevented. Hence, virus spread can be reduced once the infected person is quarantined soon after symptoms show up. In the case of the Singapore cluster the pre-symptomatic transmission was 48% , while it was 62% for the Tianjin cluster. Since the proportion of pre-symptomatic transmission is substantial, maintaining hand hygiene and physical distancing can play an important role in containing virus-spread in the community.

Source: The Hindu April 18, 2020 11:48 UTC