The first case of coronavirus disease 2019 (COVID-19) in the United States, diagnosed on January 20, 2020, was clearly related to international travel.1 Cases of infection with SARS-CoV-2 reflecting local person-to-person spread was documented on January 30, 2020, and led to escalating concern and ultimately staggered state governmental responses.2 On March 12, 2020, Wisconsin Governor Tony Evers declared a statewide public health emergency due to the COVID-19 pandemic. Orders to quarantine at home except in limited circumstances were enacted. Subsequently, the Wisconsin Department of Health Services authorized the closure of all public and private Wisconsin schools K-12 to prevent, suppress, and control the spread of SARS-CoV-2.3 Although the closure of day-care centers throughout the state was not mandated, rules for continued services were imposed. Approximately, one-third of registered day-care centers did close and many families voluntarily withdrew their children from attendance at those that remained open (J. McBride and E. Wald, e-mail communication, May 18, 2020). Although the closure of schools and the quarantine were intended to decrease the transmission of SARS-CoV-2, the impact of these measures on other, non-COVID-19, common infectious diseases has not been evaluated. This study was undertaken to determine if the quarantine imposed to diminish transmission of SARS-CoV-2 had a similar impact on other infections, which occur in children and adults. We hypothesized that both common infections transmitted by the respiratory route and those that are sexually transmitted would be decreased.
The University of Wisconsin Hospital & Clinics is a tertiary care health system located in Madison, Wisconsin, which includes the American Family Children’s Hospital, an extensive network of primary care practices, and 2 Emergency Departments located within Dane County. The diagnoses of 5 infectious diseases or syndromes [streptococcal pharyngitis, acute otitis media (AOM), infectious mononucleosis, chlamydia, and gonorrhea] were reviewed using Epic SlicerDicer function in the electronic medical record. Cases were identified via SlicerDicer queries on combinations of coded data linked by Systematized Nomenclature of Medicine-Clinical Terms using the search terms streptococcal pharyngitis, AOM infectious mononucleosis, chlamydial infection, and gonorrhea. Results were filtered to include only those patients residing in Dane County, Wisconsin, and for the timeframe between March 16th (the first day of Madison school closing in 2020) to June 10th (the last day of Madison’s school year in 2020) annually since 2015. Cases were divided into 3 age groups: (1) birth through 15 years, (2) 16–25 years, and (3) greater than 25 years. These age cohorts were chosen to highlight the various infectious disease risk factors between the young and school-age children, adults, and the adolescents/young adults that may share similar risk factors of both other groups.
Incidences of each infectious syndrome were calculated per 100,000-person years using Dane County’s 2019 estimated population of 546,695 and annual growth of 1% between the years 2015 and 2020.4 US census data were used to estimate the percentage of each age cohort: birth through 15 years, 16–25 years, and greater than 25 years.5 Based on these population estimates, the person-years for March 16 through June 10 annually from 2015 through 2019 was calculated to be 704,845. Analogously, the person-years for March 16 through June 10 for 2020 was calculated to be 145,226. The relative risk (RR) of incidence per 100,000-person years from 2015 to 2019 was compared with the RR of incidence per 100,000-person years in 2020 during the quarantine. Incidence rates were reported along with the corresponding 95% confidence intervals (CI). Changes in incidence rates between years were quantified by calculating RR, which were reported along with the corresponding 95% CI. All reported P values are 2-sided, and P < 0.05 was used to define statistical significance. Data analyses were conducted using SAS software (SAS Institute Inc., Cary, NC), version 9.4.
Incidences of streptococcal pharyngitis, AOM, and infectious mononucleosis per 100,000-person years significantly decreased during the 2020 school closures with a RR = 0.36 (P < 0.0001), RR = 0.60 (P < 0.0001), and RR = 0.84 (P = 0.0117), respectively (Fig. 1). While there was an overall increase in the incidence of chlamydia in 2020 (RR = 1.10, 95% CI: 0.99–1.22), the difference was not statistically significant. The incidence of gonorrhea increased substantially in 2020 (RR = 1.71, 95% CI: 1.38–2.11, P < 0.0001), continuing the general trend of increasing gonorrhea rates since 2015.
When the results were analyzed according to age group outcome by age varied substantially for the 5 clinical entities. For example, in children between birth and 15 years, only streptococcal pharyngitis and AOM showed significant decreases in the incidence rates in 2020 when compared with the previous 5 years. For the age group 16–25 years, significant decreases in the incidence rates ranging between 21% and 42% were observed for all clinical entities with the exception of gonorrhea. On the other hand, for the oldest cohort (≥26 y), significant decreases in the incidence rates were observed only for streptococcal pharyngitis and AOM while significant increases in the incidence rates were observed for infectious mononucleosis, chlamydia, and gonorrhea.
This review showed the expected result that a quarantine-at-home order associated with school closures resulted in a decrease in infections spread by the respiratory route but the surprising results of a simultaneous stability or increase in sexually transmitted infections. School-age children are the major reservoir for Group A Streptococcus as transmission, colonization, and infection frequently occurs within the school setting.6 Moreover, the density and frequency of colonization with the bacterial pathogens that cause AOM (Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis) increase in the setting of both symptomatic and asymptomatic viral upper respiratory tract viral infection.7 Accordingly, the absence of comingling of day care and school-age children led to the significant drop in streptococcal pharyngitis and the upper respiratory tract viral infections that contribute to AOM as expected. The effect of quarantine had a similar effect across all age groups for these 2 respiratory infections.
In contrast, the quarantine-at-home order and school closures had a different effect on diseases transmitted through sexual activity. Also named the “Kissing Disease” infectious mononucleosis is a clinical syndrome most often associated with the herpesviruses Epstein-Barr virus or cytomegalovirus and usually occurs in adolescents and young adults.8,9 These viruses are frequently spread via the exchange of bodily fluids, especially saliva, which can occur during kissing or sharing of objects such as drinking glasses or toothbrushes, activities which may also occur in supervised school settings. Gonorrhea increased in the cohort over 15 years of age, and Chlamydia was observed to increase in the age group over 25 years. This result was unanticipated as quarantining at home would be expected to preclude the acquisition of new sexual partners.
Systematized Nomenclature of Medicine-Clinical Terms search was used to identify cases via Epic electronic medical record’s SlicerDicer tool due to its ease and accuracy of filtering cases. A limitation of our study is that this electronic filter is dependent on physician clinical judgment, documentation, and coding rather than microbiologic data, which may more accurately provide the incidence of each infection. However, the current standard of care at the University of Wisconsin would be to diagnose all of these infections only when the appropriate supporting microbiologic or clinical data are present.
Activities were extremely limited during this quarantine period. Virtually all businesses, schools, cultural (theaters, movies, concerts, sports events), and other recreational activities (parks, playgrounds, etc.) were closed or not permitted. Leaving the home was sanctioned only for work related (if essential) activities and purchase of groceries and pharmaceuticals. As a result of these measures, the incidence of 2 common infections of childhood, streptococcal pharyngitis, and AOM, decreased. However, these efforts did not have the same effect on sexually transmitted infections more commonly seen in older teens and adults. These data argue that quarantine may mitigate the spread of the infectious diseases of the classroom but may not have the same impact as those spread in the bedroom.
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