Demographic and epidemiological factors associated with COVID-19 superspreading persons in Gangwon province

Superspreading persons (SSPs) drive marked heterogeneity in SARS-CoV-2 transmission, yet quantitative evidence on their determinants in community settings remains limited.

To quantify the impact of SSPs and identify demographic, virologic, and contextual correlates of superspreading in Gangwon Province, Korea.

We analysed province-wide epidemiological investigation records for laboratory-confirmed COVID-19 from 21 February 2020 to 31 January 2022. Transmission networks linking index and secondary cases were reconstructed. Superspreaders were prespecified as individuals generating ≥7 secondary infections. Offspring counts were modelled with a negative binomial distribution; multivariable logistic regression estimated adjusted odds ratios for age, vaccination, symptoms at diagnosis, PCR cycle-threshold (Ct), occupation, exposure setting, and viral variant based on specimen date.

Among 15,300 community-acquired cases, offspring counts followed a negative binomial distribution(κ = 0.36). Most cases generated ≤6 secondaries, whereas 164 cases (1.1%) met the superspreader criterion and accounted for 1,571 downstream infections (11.3%). Higher odds of superspreading were observed among ages 0-19 (aOR 1.86) and 40-59 (1.84), the unvaccinated (1.64), those symptomatic at diagnosis (2.13), individuals with Ct <16.0 (2.54) or 16.0-23.9 (2.15), white-collar workers (1.68), same-facility exposures (2.39), and cases with an unknown source of infection (3.91). Superspreading odds also varied across variant-dominant periods inferred from specimen dates, although confidence intervals included unity.

SARS-CoV-2 transmission in Gangwon was highly overdispersed, with a small minority of cases responsible for a disproportionate share of spread. Targeted vaccination, rapid isolation of symptomatic or low-Ct index cases, and strengthened controls in high-risk workplaces and shared facilities may help blunt future superspreading.