While no one wants to think of themselves as a super spreader of Covid-19, a new study has given support to the idea that “silent transmission” — the spread of virus by someone with no obvious symptoms — could be responsible for half of all novel coronavirus cases in the United States.
More than one-third of silent infections would need to be identified and isolated to suppress a future outbreak, the study estimated.
According to Tuesday morning’s Johns Hopkins University data, 31 states are reporting higher rates of new Covid-19 cases this week compared to last week. Another 15 states are holding steady and only four are trending down, according to the data.
“We are still knee-deep in the first wave of this,” said White House Coronavirus Task Force member Dr. Anthony Fauci during a Facebook/Twitter livestream event on Monday.
“And I would say this would not be considered a wave. It was a surge, or a resurgence of infections superimposed upon a baseline … that really never got down to where we wanted to go,” Fauci said. “So it’s a serious situation that we have to address immediately.”
Asymptomatic or presymptomatic spread
Alison Galvani, director of Yale University’s Center for Infectious Disease Modeling and Analysis, and colleagues used coronavirus transmission models to determine the extent to which silent transmission contributes to the spread of Covid-19.
They based the study on existing research, which indicates asymptomatic infections account for 17.9% to 30.8% of all infections.
Assuming 17.9% of cases are asymptomatic, the team found that presymptomatic people would account for 48% of transmission, and asymptomatic people would account for 3.4% of transmission.
If 30.8% of cases are asymptomatic, they found that presymptomatic people would be responsible for 47% of transmitted cases and asymptomatic people would account for 6.6% of transmission, respectively.
The model assumes Covid-19 may be most contagious during the presymptomatic stage, which is uncommon for a respiratory infection. The team found that even immediate isolation of all symptomatic cases would not be enough to get the spread under control.
To suppress a future outbreak below 1% of the population, the study found it would be necessary to identify and isolate more than one-third of silent transmitters, in addition to all symptomatic cases.
Researchers emphasized the need for both testing and contact tracing to safely lift the current social distancing and stay-at-home restrictions.
What you can do
Even with a mask, stay away from large crowds and 6 feet from anyone not in your “bubble.” If you do, socialize, try to limit it to outdoor locations with excellent air circulation and filtration. Keep your hands away from your face.
And take a lesson from the mistakes of Typhoid Mary: Wash your hands with soap and water frequently, for a minimum of 20 seconds. And if some public health officials tell you that you need to take precautions, don’t ignore them. While Mary may have died alone after 26 years of forced quarantine, there’s still time for you to help keep yourself, your loved ones and the strangers around you safe.