"... there are key discrepancies between people who have no symptoms, those who are presymptomatic and those who are subclinical with less severe symptoms, which can make studying the true amount of asymptomatic carriers of COVID-19 extremely challenging.
"We still don't understand the role of people who have no symptoms the entire time [they're infected] versus people that have very, very mild symptoms that are misclassified as having no symptoms, versus people that have no symptoms for the first few days and then go on to develop them," he said.
"So, when we heard the WHO say that people without symptoms rarely transmit this infection, an eyebrow went up, because we certainly know that there are different types of people without symptoms and it's a little more complicated than what they had reported."