Testing and isolation to prevent overloaded health care facilities and to reduce death rates in the SARS-CoV-2 pandemic in Italy

Background During the first wave of COVID-19, hospital and intensive care unit beds got overwhelmed in Italy leading to an increased death burden. Based on data from Italian regions, we disentangled the impact of various factors contributing to the bottleneck situation of health care facilities, not well addressed in classical SEIR-like models. A particular emphasis was set on the dark figure, on the dynamically changing hospital capacity, and on different testing, contact tracing, quarantine strategies. Methods We first estimated the dark figure for different Italian regions. Using parameter estimates from literature and, alternatively, with parameters derived from a fit to the initial phase of COVID-19 spread, the model was optimized to fit data (infected, hospitalized, ICU, dead) published by the Italian Civil Protection. Results We showed that testing influenced the infection dynamics by isolation of newly detected cases and subsequent interruption of infection chains. The time-varying reproduction number ( R t) in high testing regions decreased to < 1 earlier compared to the low testing regions. While an early test and isolate (TI) scenario resulted in up to ∼ 32% peak reduction of hospital occupancy, the late TI scenario resulted in an overwhelmed health care system. Conclusions An early TI strategy would have decreased the overall hospital accessibility drastically and, hence, death toll (∼ 45% reduction in Lombardia) and could have mitigated the lack of health care facilities in the course of the pandemic, but it would not have kept the hospitalization amount within the pre-pandemic hospital limit. We showed that contact tracing and quarantine without testing would have a similar effect and might be an efficient strategy when sufficient test capacities are not available. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 101003480 and the Initiative and Networking Fund of the Helmholtz Association. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: All relevant ethical guidelines have been followed. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data are available and referenced in the manuscript.