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Purpose Fever is one of the most typical clinical symptoms of coronavirus disease 2019 (COVID-19), and non-contact infrared thermometers (NCITs) are commonly used to screen for fever. However, there is a lack of authoritative data to define a “fever” when an NCIT is used and previous studies have shown that NCIT readings fluctuate widely depending on ambient temperatures and the body surface site screened. The aim of this study was to establish cut-off points for normal temperatures of different body sites (neck, forehead, temples, and wrist) and investigate the accuracy of NCITs at various ambient temperatures to improve the standardization and accuracy of fever screening. Patients and Methods A prospective investigation was conducted among 904 participants in the outpatient and emergency departments of Chengdu Women’s and Children’s Central Hospital. Body temperature was measured using NCITs and mercury axillary thermometers. A receiver operating characteristic curve was used to determine the accuracy of body temperature detection at the four body surface sites. Data on participant characteristics were also collected. Results Among the four surface sites, the neck temperature detection group had the highest accuracy. When the neck temperature was 37.35°C as the optimum fever diagnostic threshold, the sensitivity was 0.866. The optimum fever diagnostic thresholds for forehead, temporal, and wrist temperature were 36.65°C, 36.65°C, and 36.75°C, respectively. Moreover, triple neck temperature detection had the highest sensitivity, up to 0.998, whereas the sensitivity of triple wrist temperature detections was 0.949. Notably, the accuracy of NCITs significantly reduced when the temperature was lower than 18°C. Conclusion Neck temperature had the highest accuracy among the four NCIT temperature measurement sites, with an optimum fever diagnostic threshold of 37.35°C. Considering the findings reported in our study, we recommend triple neck temperature detection with NCITs as the fever screening standard for COVID-19.

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IntroductionCoronavirus disease 2019 has become a major global public health concern in December 2019. However, finding and excluding close contacts of COVID-19 infectors is a critical but difficult issue. This study aimed to introduce a new method of epidemiological investigation named space–time companions, which was adopted in Chengdu, China, in November 2021.MethodsAn observational investigation was conducted during a small outbreak of COVID-19 in Chengdu, China in November 2021. A new method of epidemiological investigation called space–time companion was adopted in this outbreak, which was defined as the one who stayed in the same spatiotemporal grid (range: 800 m * 800 m) with the confirmed COVID-19 infector for more than 10 min in the last 14 days. A flow chart was used to describe the screening process of space–time companions in detail and illustrate the space–time companion epidemic management method.ResultsThe COVID-19 epidemic outbreak in Chengdu was effectively controlled for approximately one incubation period (14 days). After four rounds of space–time companions screening, more than 450,000 space–time companions were screened, including 27 COVID-19 infectors. Moreover, in the subsequent rounds of nucleic acid testing for all people in the city, no infected person were found proving the end of this epidemic outbreak.ConclusionThe space–time companion provides a new idea for screening close contacts of the COVID-19 infector and other similar infectious diseases, which can serve as a supplement to traditional epidemiological history surveys to verify and avoid missing close contacts.