Community SARS-CoV-2 Surge and Within-School Transmission

OBJECTIVES: When the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic began, experts raised concerns about in-person instruction in the setting of high levels of community transmission. We describe secondary transmission of SARS-CoV-2 within North Carolina (NC) K-12 school districts during a winter surge to determine if mitigation strategies can hinder within-school transmission. METHODS: From 10/26/2020–02/28/2021, 13 NC school districts participating in the ABC Science Collaborative were open for in-person instruction, adhered to basic mitigation strategies, and tracked community- and school-acquired SARS-CoV-2 cases. Public health officials adjudicated each case. We combined these data with that from August 2020 to evaluate the effect of the SARS-CoV-2 winter surge on infection rates, as well as weekly community- and school-acquired cases. We evaluated the number of secondary cases generated by each primary case, as well as the role of athletic activities in school-acquired cases. RESULTS: More than 100,000 students and staff from 13 school districts attended school in-person; of these, 4,969 community-acquired SARS-CoV-2 infections were documented by molecular testing. Through contact tracing, NC local health department staff identified an additional 209 infections among >26,000 school close contacts (secondary attack rate <1%). Most within-school transmissions in high schools (75%) were linked to school-sponsored sports. School-acquired cases slightly increased during the surge; however, within-school transmission rates remained constant, from pre-surge to surge, with approximately 1 school-acquired case for every 20 primary cases. CONCLUSIONS: With adherence to basic mitigation strategies, within-school transmission of SARS-CoV-2 can be interrupted, even during a surge of community infections

The evolution of virus diseases: their emergence, epidemicity, and control

The evolution of virus diseases, both their emergence and disappearance, involves complex interactions between the agent, the host, and the environment. These themes are illustrated by three examples, poliomyelitis of humans, bovine spongiform encephalopathy of cattle, and AIDS of humans. Emergence may be due to evolution of the virus genome, such as probably occurred in parvovirus infection of dogs and human immunodeficiency virus infection of humans. However, emergence of some new viral diseases can be traced to host or environmental factors with no change in the agent. Poliomyelitis, an enteric infection, probably emerged as an epidemic disease due to improvements in personal hygiene and public sanitation which led to a delay in the occurrence of initial infections from the perinatal period (when maternal antibody protected against paralysis) to later childhood when passive immunity had waned. Bovine spongiform encephalopathy is a common source epidemic which was transmitted through nutritional supplements which became contaminated due to a change in the method of production of bone meal supplements in rendering plants. The reduction or disappearance of virus diseases usually involves human intervention, as exemplified by immunization for smallpox and other virus diseases of humans and animals. Naturally occurring immunity may lead to fadeout of a virus as seen with measles in isolated island populations. Evolution of a virus can also result in waning of a disease as seen with myxomatosis among rabbits in Australia. The evolution of virus diseases is a provocative scientific topic and carries lessons relevant to the control of important diseases of humans, animals, and plants