'Super-spreaders' caused up to 20% of all COVID-19 cases in Georgia, study finds

Aug. 20 (UPI) -- About 20% of all COVID-19 infections in Georgia during the early stages of the outbreak were directly linked with 2% of the cases, according to a study published Thursday by the Proceedings of the National Academy of Sciences.

The findings indicate that "super-spreading" of the virus was widespread in the state, particularly in rural areas, the researchers said.

"Super-spreading can contribute to explosions of transmission, even when we are seeing the numbers of new cases declining," study co-author Max Lau, an assistant professor of biostatics and bioinformatics at Emory University's Rollins School of Public Health, told UPI.

"Everyone should be mindful of maintaining social distancing so that super-spreading can be curtailed," he said.

Super-spreading is a phenomenon in which certain individuals disproportionately infect a large number of people. Several "super-spreader" events have been recorded across the country since the start of the pandemic, according to Lau and his colleagues.

For this study, the researchers from Emory University reviewed data on nearly 10,000 confirmed cases of COVID-19 reported to the Georgia Department of Public Health between March 1 and May 3.

The cases were concentrated in five counties across the state, the researchers said. They were Cobb, DeKalb, Gwinnett and Fulton in the metro Atlanta area and Dougherty in the more rural southwest region.

The R-number -- or the average number of people each confirmed case infects -- was 3.3 across all five countries, but highest, at 5.2, in the rural Dougherty, the data showed.

That figure suggests that super-spreaders may have been responsible for the outbreak in that county, which saw more than 1,600 confirmed COVID-19 cases in March, April and May -- or roughly the same number as Cobb County, which has a population roughly eight times higher, the researchers said.

In addition, in all five counties, "non-elderly" COVID-19 cases -- those involving people aged 60 years and younger -- were up to three times more contagious than older adults, according to the researchers.

However, "super-spreading is mostly likely to be driven by behaviors and circumstances" -- not wearing a mask or social distancing -- "regardless of age," Lau said.