A study of SARS-COV-2 outbreaks in US federal prisons: the linkage between staff, incarcerated populations, and community transmission

Abstract

Background: Since the novel coronavirus SARS-COV-2 was first identified to be circulating in the US on January 20, 2020, some of the worst outbreaks have occurred within state and federal prisons. The vulnerability of incarcerated populations, and the additional threats posed to the health of prison staff and the people they contact in surrounding communities underline the need to better understand the dynamics of transmission in the inter-linked incarcerated population/staff/community sub-populations to better inform optimal control of SARS-COV-2.

Methods: We examined SARS-CoV-2 case data from 101 non-administrative federal prisons between 5/18/2020 to 01/31/2021 and examined the per capita size of outbreaks in staff and the incarcerated population compared to outbreaks in the communities in the counties surrounding the prisons during the summer and winter waves of the SARS-COV-2 pandemic. We also examined the impact of decarceration on per capita rates in the staff/incarcerated/community populations.

Results: For both the summer and winter waves we found significant inter-correlations between per capita rates in the outbreaks among the incarcerated population, staff, and the community. Over-all during the pandemic, per capita rates were significantly higher in the incarcerated population than in both the staff and community (paired Student's t-test p = 0.03 and p < 0.001, respectively). Average per capita rates of incarcerated population outbreaks were significantly associated with prison security level, ranked from lowest per capita rate to highest: High, Minimum, Medium, and Low security. Federal prisons decreased the incarcerated population by a relative factor of 96% comparing the winter to summer wave (one SD range [90%,102%]). We found no significant impact of decarceration on per capita rates of SARS-COV-2 infection in the staff community populations, but decarceration was significantly associated with a decrease in incarcerated per capita rates during the winter wave (Negative Binomial regression p = 0.015).

Conclusions: We found significant evidence of community/staff/incarcerated population inter-linkage of SARS-COV-2 transmission. Further study is warranted to determine which control measures aimed at the incarcerated population and/or staff are most efficacious at preventing or controlling outbreaks.

Keywords: Community; Coronavirus; Decarceration; Disease intervention strategies; Inmates; Pandemic; Prisons; SARS-COV-2.

Fig. 1

Per capita prevalence of SARS-COV-2 infections in incarcerated prison population and staff summed over non-administrative federal prisons for which the staff population is known, along with the per capita SARS-COV-2 incidence summed over the surrounding counties. For ease of comparison of the temporal patterns, the area under the curves are normalized to sum to one (however, in reality the staff and incarcerated per capita rates are around 4 times the community per capita rates, as shown in Table 1). The vertical black dotted line represents the nominal cut-off between the two waves at the end of September, 2020. Note that temporal patterns in incarcerated individuals and staff per capita rates are dominated by just a few prisons; seven prisons account for over 50% of cases in both staff and incarcerated individuals

Fig. 2

Correlogram matrix showing the correlations between per capita rates of SARS-COV-2 cases in incarcerated individuals, staff in federal non-administrative prisons, and in the surrounding counties during the summer and winter waves of the pandemic. Absolute correlations larger than 0.20 are significant to p < 0.05 (two-sided t-test). The more diagonal and more intensely colored the ellipsoid, the larger the absolute correlation (as shown in the scale to the right), with blue upward slanted ellipsoids representing positive correlatiosn, and red downward slanted ellipsoids representing negative correlations

Fig. 3

Distribution of mean SARS-COV-2 per capita rates in incarcerated and staff populations by security level for non-administrative federal prisons, over-all between May 18, 2020 to Jan 31, 2021 (top row) and for the summer and winter waves (second and third row). The vertical bars represent the standard error on the means. The dotted horizontal line represents the average over all security levels. Significant relationship to security level are seen in b) and d) (population standardized Negative Binomial factor regression p < 0.05 in both cases)