He helped Covid kill the Small Scientific Roof Epidemiologists have long seen that most respiratory insects need a close relationship to spread. However, in this small space, a lot can happen. A sick person may cough up drops on your face, emit small aerosols that you breathe or give your hand so you can rub your nose. Any of these mechanisms can transmit the virus. “Technically, it’s very difficult to differentiate and see what causes the infection,” Mar says. In long-distance infections, only the smallest particles can be to blame. Up close, however, particles of all sizes were at stake. However, over the decades, drops were blamed as the main culprit.