The Journal of the American Medical Association just reported that 59% of new CoV-2 infections are likely caused by infected people who do not show COVID-19 symptoms. This conclusion is based on the results of a decision analytical model that assessed the spread from pre-symptomatic, never-symptomatic and symptomatic people infected with CoV-2. 35% of viral transmission came from pre-symptomatic people, and 24% from people who never develop symptoms.
This means that until the vaccines are widely disseminated, identifying and isolating people with COVID-19 will be much less effective at controlling the spread of the virus than previously thought. Effective control of the disease still requires social isolation measures such as wearing face masks indoors, distancing from others, hand hygiene, and limiting indoor contact with other people.