Study Finds “Silent Spreaders” May Be Responsible for Half of Covid-19 Cases


As the first known healthy carrier of bacterial disease, which is transmitted by a toxin in the stool, Mallon refused to believe that she was an asymptomatic conduit for typhoid fever. She declined to give stool samples to authorities and continued to spread the bacteria through its unhealthy forms until she was caught and quarantined twice for a total of 26 years, dying alone without friends.

While no one wants to think of themselves as a Covid-19 super diffuser, a new study has supported the idea that “silent transmission,” the spread of the virus by someone with no obvious symptoms, could be responsible for half of all new cases of coronavirus in the United States.

The study estimated that more than a third of silent infections would have to be identified and isolated to suppress a future outbreak.

According to Johns Hopkins University data on Tuesday morning, 31 states report higher rates of new Covid-19 cases this week compared to last week. Another 15 states remain stable and only four have a downward trend, according to the data.

“We are still knee deep in the first wave of this,” White House Coronavirus Task Force member Dr. Anthony Fauci said Monday during a live Facebook / Twitter event.

“And I would argue that this would not be considered a wave. It was a wave or a resurgence of infections superimposed on a baseline … that never really got where we wanted to go,” Fauci said. “Therefore, it is a serious situation that we must address immediately.”

Asymptomatic or presymptomatic spread

Alison Galvani, director of the Center for Modeling and Analysis of Infectious Diseases at Yale University, and her colleagues used coronavirus transmission models to determine the extent to which silent transmission contributes to the spread of Covid-19.

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They based the study on existing research, which indicates that 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 that Covid-19 may be more contagious during the presymptomatic stage, which is rare in a respiratory infection. The team found that even immediate isolation of all symptomatic cases would not be enough to control the spread.

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To suppress a future outbreak below 1% of the population, the study found that more than a third of silent transmitters would need to be identified and isolated, in addition to all symptomatic cases.

The researchers emphasized the need for testing and contact tracing to safely lift the current social estrangement and restrictions of staying home.

What you can do

Believe in the power of masks: Recent studies show that they work if used correctly. Using them when you are in public or with people who are not in your “quarantine bubble,” even if you don’t have symptoms of infection, will help prevent silent transmission.

Even with a mask, stay away from large crowds and within 6 feet of anyone who is not in your “bubble”. If you socialize, try to limit it to outdoor places with excellent air circulation and filtration. Keep your hands away from your face.

And take a lesson from typhoid mistakes: Wash your hands with soap and water frequently, for at least 20 seconds. And if some public health officials tell you to take precautions, don’t ignore them. While Mary may have died alone after 26 years of forced quarantine, there is still time for her to help keep herself, her loved ones, and the strangers around her safe.

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