Cases where an infected person spread COVID-19 to eight or more people have taken place repeatedly in metro Atlanta's largest counties, a recent Emory University study found, highlighting how a single gathering can drive the spread of the virus.
Scores of instances of what scientists call superspreading took place from March through early May in Cobb, DeKalb, Fulton and Gwinnett counties and hard-hit Dougherty in south Georgia, researchers found. In all, about 2% of infected people may have directly infected 20% of all those with confirmed cases. A handful likely infected 15 or more people.
The age group that spreads the novel coronavirus to the most people is not Georgia’s elderly, some 2,500 of whom have died during the pandemic. On average, children and younger adults under the age of 60 are nearly 2.4 times more transmissible, the study found.
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As Fourth of July weekend approaches and cases of the virus grow exponentially in Georgia, the research is a reminder of the importance of avoiding large gatherings, wearing masks, and following other measures that public health experts have advocated for since the beginning of the pandemic, said Emory University Assistant Professor Kristin Nelson, one of the study’s co-authors
“We know that these events happen. We also know how to prevent them,” Nelson said. Researchers have found similar superspreading patterns in other countries.
Georgia encourages residents to wear masks but does not require it. Gov. Brian Kemp toured south Georgia before the Fourth of July weekend to encourage voluntary mask use. He started wearing them during press conferences in recent weeks.
“The best way to avoid any event that could expose individuals would be to continually follow the prevention guidance, like socially distancing as much as possible, wearing a mask to protect others, and washing hands often,” said Chad Wasdin, a spokesman for the Gwinnett, Newton & Rockdale County Health Departments. “We know these measures work, and following these guidelines are important now more than ever.”
Emory researchers based their conclusions on data collected by the Georgia Department of Public Health for more than 9,500 cases and mobile phone usage from Facebook. It does not include the identities of individuals. Researchers did not interview people involved in superspreading events.
The Emory study is in pre-print, which means it has yet to be peer reviewed.
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There is no official criteria for the number of people who must be infected before scientists classify an incident as a superspreading event. Generally, these take place when a person infects many more people than the disease does on average.
State DPH epidemiologists track all outbreaks, said spokeswoman Nancy Nydam, but not all of them involve superspreaders.
Any gathering in a crowded room where people fail to wear masks and there is poor ventilation can create a superspreading event, Nelson said. Such instances are less about how infectious any individual is than the conditions under which he or she comes into contact with others.
“They could occur in a nursing home or in a bar down the street that is crowded. They could occur just about everywhere,” Nelson said.
Superspreading is gaining attention for its dramatic and deadly impact. One Centers for Disease Control and Prevention study detailed a Washington state case where a single person with symptoms may have infected 53 people during a choir practice. Two died.
In Dougherty, public health experts think two funerals set off a deadly outbreak of the novel coronavirus that overwhelmed hospitals in the region.
Locally, few suspected superspreading events have been disclosed. Post-graduation celebrations are believed to be behind an outbreak among Lovett School students in Buckhead that infected 18 people, according to Channel 2 Action News, though it has not been publicly described as such an instance.
Still, the Emory study and others found superspreading events take place repeatedly and are integral to the spread of this virus.
Researchers identified more than a dozen likely superspreading cases in Cobb County, though a spokeswoman for its health department said that it had identified no superspreading events.
County case investigators ask people who test positive where they visited and work and who they have come into close contact with. But it’s possible that infected people are not giving investigators all the details they ask for, spokeswoman Valarie Crow said.
“It’s up to the case to be forthcoming/specific with us,” she wrote.
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