Rapid Increase in Suspected SARS-CoV-2 Reinfections, Clark County, Nevada, USA, December 2021

Abstract

Genetic differences between SARS-CoV-2 variants raise concerns about reinfection. Public health authorities monitored the incidence of suspected reinfection in Clark County, Nevada, USA, during March 2020-March 2022. Suspected reinfections, defined as a second positive PCR test collected >90 days after an initial positive test, were monitored through an electronic disease surveillance system. We calculated the proportion of all new cases per week that were suspected reinfections and rates per 1,000 previously infected persons by demographic groups. The rate of suspected reinfection remained <2.7% until December 2021, then increased to ≈11%, corresponding with local Omicron variant detection. Reinfection rates were higher among adults 18-50 years of age, women, and minority groups, especially persons identifying as American Indian/Alaska Native. Suspected reinfection became more common in Clark County after introduction of the Omicron variant, and some demographic groups are disproportionately affected. Public health surveillance could clarify the SARS-CoV-2 reinfection burden in communities.

Keywords: COVID-19; Nevada; Omicron variant; SARS; SARS-CoV-2; United States; coronavirus; coronavirus disease; reinfection; respiratory infections; severe acute respiratory syndrome coronavirus 2; viruses; zoonoses.

Figure 1

SARS-CoV-2 cases and suspected reinfections, Clark County, Nevada, USA, March 2020–March 2022. Dotted lines show timeframe for identification of Alpha, Delta, and Omicron SARS-CoV-2 variants in Clark County. New cases were defined as a first positive SARS-CoV-2 PCR test for a person. Suspected reinfections were defined as a second positive SARS-CoV-2 PCR test collected >90 days after a person’s first positive PCR test.

Figure 2

Suspected third SARS-CoV-2 infections, Clark County, Nevada, USA, March 2021–March 2022. Dotted lines show timeframe for identification of Delta and Omicron SARS-CoV-2 variants in Clark County. Suspected third infections were defined as a third positive PCR test collected >90 days after a second positive test collected >90 days after a person’s initial positive PCR test.