Fevers Are Rarest in the Morning: Could We Be Missing Infectious Disease Cases by Screening for Fever Then?

Harding, C.; Pompei, F.; Bordonaro, S. F.; McGillicuddy, D. C.; Burmistrov, D.; Sanchez, L. D.

Body temperatures are less likely to reach the fever range in the morning, but it is unknown how this affects practice during disease outbreaks. We retrospectively investigated fever-range temperatures ([≥]100.4{degrees}F, [≥]38.0{degrees}C) during seasonal influenza outbreaks and the 2009 H1N1 (swine flu) pandemic, which have recently been used as preparatory models for coronavirus disease 2019 (COVID-19). Our analyses included a nationally representative sample of records from adult visits to US emergency departments (n=202,181) and data from a Boston emergency department (n=93,225). Fever-range temperatures were about half as common in the morning as in the evening, suggesting that morning temperatures can be much less diagnostic, and that revisions may be needed to the practice of once-daily temperature screens at morning arrival to workplaces and schools. Twice-daily screens could be a simple solution, but similar research is still needed on fevers in COVID-19 itself.