LOS ANGELES - Asymptomatic individuals are believed by many scientists to be contributing to the rapid spread of the novel coronavirus, and a new study indicates that people with COVID-19 but who do not show symptoms may be behind most infections.Published in the Proceedings of the National Academy of Sciences, the July 6 study refers to the phenomena of COVID-19 infections by asymptomatic and presymptomatic individuals as “silent transmission.”The study says that even if symptomatic cases are isolated — such as a person being quarantined until they have recovered or tested negative for the virus — “a vast outbreak may nonetheless unfold.””We further quantified the effect of isolating silent infections in addition to symptomatic cases,.