Studies show that carriers with no symptoms may have higher viral loads and spread infection more widely than those who show symptoms.
Dr. Sandra Ciesek, director of the Institute of Medical Virology in Frankfurt, Germany, tested 24 passengers who had just flown in from Israel. Seven tested positive for coronavirus. Four of those had no symptoms, and Ciesek was surprised to find that the viral load of the specimens from the asymptomatic patients was higher than the viral load of the specimens from the three patients who did have symptoms.
Several experts interviewed by CNN said while it’s unclear exactly what percentage of the transmission in the outbreak is fueled by people who are obviously sick versus those who have no symptoms or very mild symptoms, it’s become clear that transmission by people who are asymptomatic or mildly symptomatic is responsible for more transmission than previously thought.
“We now know that asymptomatic transmission likely [plays] an important role in spreading this virus,” said the director of the Center for Infectious Disease Research and Policy at the University of Minnesota. It’s “absolutely clear” that asymptomatic infection “surely can fuel a pandemic like this in a way that’s going to make it very difficult to control.”
In an article two weeks ago in the New England Journal of Medicine, Bill Gates, expressed concern about the spread of the disease by people who haven’t yet developed symptoms, or who are only a bit sick.
“There is also strong evidence that it can be transmitted by people who are just mildly ill or even pre-symptomatic. That means COVID-19 will be much harder to contain than the Middle East respiratory syndrome or severe acute respiratory syndrome (SARS), which were spread much less efficiently and only by symptomatic people,” he wrote, using the scientific word for the disease caused by the virus.