Use of surveillance data to elucidate household clustering of SARS-CoV-2 in Fulton County, Georgia a major metropolitan area

Abstract

Background: Households are important for SARS-CoV-2 transmission due to high intensity exposure in enclosed spaces over prolonged durations. We quantified and characterized household clustering of COVID-19 cases in Fulton County, Georgia.

Methods: We used surveillance data to identify all confirmed COVID-19 cases in Fulton County. Household clustered cases were defined as cases with matching residential address. We described the proportion of COVID-19 cases that were clustered, stratified by age over time and explore trends in age of first diagnosed case within households and subsequent household cases.

Results: Between June 1, 2020 and October 31, 2021, 31,449(37%) of 106,233 cases were clustered in households. Children were the most likely to be in household clusters than any other age group. Initially, children were rarely (∼ 10%) the first cases diagnosed in the household but increased to almost 1 of 3 in later periods.

Discussion: One-third of COVID-19 cases in Fulton County were part of a household cluster. Increasingly children were the first diagnosed case, coinciding with temporal trends in vaccine roll-out among the elderly and the return to in-person schooling in Fall 2021. Limitations include restrictions to cases with a valid address and unit number and that the first diagnosed case may not be the infection source for the household.

Keywords: Covid-19; Household transmission; Surveillance.

Fig. 1

Temporal trend in the proportion of diagnosed cases in Fulton County, Georgia (with a valid residential household address and a valid unit number), that were identified in household clusters stratified by the month of positive sample collection date (dark blue line), with 95% confidence interval around the point estimate. A bar chart of monthly confirmed cases in Fulton County is provided for reference. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 2

Temporal trend in the proportion of diagnosed cases (with a valid residential household address and a valid unit number) in Fulton County, Georgia, that were identified in household clusters stratified by month of positive sample collection date (x-axis) and by age group.

Fig. 3

Bubble plot of distribution of clusters across different cluster age profiles where the x-axis is the age of first diagnosed case in the household cluster, y-axis is the age of subsequent secondary diagnosis in the household cluster, the size of bubble represents number of clusters by each age pairing of first diagnosed case and subsequent cases and the density representing more common cluster age profiles (on the diagonal between cases of the same age in the same household and the two off-diagonal “wings” representing intergenerational clusters).