Case Series; Prospective Cohort
Study population and setting
This was a descriptive study carried out by the Kentucky Department of Public Health at a skilled nursing facility which had two COVID-19 outbreaks (in July 2020 and October 2020). In the first outbreak, which lasted from July 16 to August 11, 2020, 20 of 115 (17.4%) residents and five of the 143 health care professionals (3.5%) tested positive for SARS-CoV-2. Initially, testing was based on symptoms and contact, but was expanded to all residents and staff. Overall, eight residents with COVID-19 were hospitalized, of whom five died. Following the first outbreak, the facility monitored staff and residents for symptoms and tested symptomatic individuals, while health care personnel were tested at least every two weeks. Tests conducted in September and from October 1 to October 29 on facility residents and staff were all negative. On October 30, 2020, two symptomatic residents received positive test results, and all residents and staff were tested twice weekly. Subsequently, 85 of 114 (74.6%) residents and 43 of 146 (29.5%) personnel received positive results, of whom 15 residents died between October 30 and December 7, 2020. No health care professionals died during either outbreak.
Summary of Main Findings
Five permanent residents of the facility had positive reverse-transcription PCR SARS-CoV-2 tests at both outbreaks, even though all had at least four consecutive negative RT-PCR SARS-CoV-2 tests after the first outbreak. The five individuals ranged in age from 67 to 99 years; four were women, and all had more than three chronic underlying health conditions, although none had an immunosuppressive condition or were taking immunosuppressive medication. During the first outbreak, three of these individuals were asymptomatic, while two had mild symptoms. During the second outbreak, three of the five individuals had a roommate who tested positive to SARS-CoV-2, but no direct route of exposure was identified for the other two. All five experienced more severe disease in the second outbreak and one died. Investigators speculated that the findings could be due to true re-infection resulting from waning immunity in this aging population, or as a result of mild/asymptomatic cases not triggering a robust immune response to prevent reinfection. Alternatively, investigators noted the potential of false positive results during the first outbreak. However, they noted that the cycle threshold for all five of these residents met the cutoff for limit of detection during the first outbreak, supporting infection.
Reverse-transcription PCR testing was used to confirm diagnoses during both outbreaks. Testing of all residents, including those who were asymptomatic, also strengthens our understanding of reinfection among residents overall.
The investigators provided solid evidence to support their claim that residents were reinfected (versus experiencing prolonged disease). This evidence could have been bolstered even further by ruling out false positives during the first outbreak — with either repeat RT-PCR, antibody tests, or both — and using phylogenetic analyses to detect differences in the infecting virus. However, investigators were unable to ascertain phylogenetic strains between outbreaks because test samples had not been preserved and no further testing was performed on the residents until 10 or more days after the first RT-PCR positive test.
This study highlights the importance of continued infection prevention and control strategies, even among persons with previous COVID-19 diagnosis.
This review was posted on: 26 March 2021