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BackgroundMost respiratory viruses show pronounced seasonality, but for SARS-CoV-2 this still needs to be documented. MethodsWe examined the disease progression of COVID-19 in 6,914 patients admitted to hospitals in Europe and China. In addition, we evaluated progress of disease symptoms in 37,187 individuals reporting symptoms into the COVID Symptom Study application. FindingsMeta-analysis of the mortality risk in eight European hospitals estimated odds ratios per one day increase in the admission date to be 0.981 (0.973-0.988, p<0.001) and per increase in ambient temperature of one degree Celsius to be 0.854 (0.773-0.944, p=0.007). Statistically significant decreases of comparable magnitude in median hospital stay, probability of transfer to Intensive Care Unit and need for mechanical ventilation were also observed in most, but not all hospitals. The analysis of individually reported symptoms of 37,187 individuals in the UK also showed the decrease in symptom duration and disease severity with time. InterpretationSeverity of COVID-19 in Europe decreased significantly between March and May and the seasonality of COVID-19 is the most likely explanation. Mucosal barrier and mucociliary clearance can significantly decrease viral load and disease progression, and their inactivation by low relative humidity of indoor air might significantly contribute to severity of the disease.
RESUMO
Objectiveto quantitatively assess disturbances of sweet, sour and salty and bitter tastes in a group of young, asymptomatic or oligosymptomatic COVID-19 patients; establish a reliable, sensitive and specific test that can diagnose COVID-19 on the basis of taste disorders and publish the results according to STARD 2015 statement (Standards for Reporting Diagnostic Accuracy). Designcase-control study Settingisolated rooms in the Central Clinical Hospital of the Ministry of the Interior and Administration in Warsaw (which had been transformed into an infectious hospital) and a dormitory in one of Warsaw universities. Participants52 SARS-CoV-2 positive (51 men, mean age 21.7 years) and 36 negative students (34 men, mean age 20.8 years). Main outcome measuresa gustatory function assessment (sweet, salty, sour and bitter taste), with flavour concentrations established previously in healthy subjects was conducted for all subjects. Each participant received one tasteless reference and nine flavour tablets with sucrose concentrations of 40, 80 and 106.4 mg/ml; NaCl at 13.5, 17 and 27 mg/ml; ascorbic acid at 6.25 and 12.5 mg/ml and grapefruit extract at 40 mg/ml. Resultsthe only taste that was impaired significantly more frequently in COVID-19 patients was the sweet taste at the lowest flavour concentration (40 mg/ml, p = 0.002). Different screening and diagnostic models were constructed using the examined variables. The highest accuracy screening test consisted of the positive result of a three-question questionnaire (self-reported loss of taste, self-reported loss of smell, or fever within the last month (positive if at least one present) and/or ageusia of sweet taste at a sucrose concentration of 40 mg/ml. The sensitivity of the model was 94% with a specificity of 55%. The highest accuracy diagnostic test consisted of ageusia of sweet taste at a sucrose concentration of 106.4 mg/ml or/and ageusia of salty taste at an NaCl concentration of 13.5 or 17 mg/ml. The specificity of the test was found to be 100%, and the sensitivity was 34%. Conclusionas the most effective way of controlling the present pandemic involves testing the wider population for symptomatic, oligosymptomatic and asymptomatic carriers of SARSCoV-2 and isolating or hospitalising infected subjects, in the present study, an inexpensive, simple, fast and sensitive (94%) screening test that can be used for such a purpose is proposed. In addition, a specific (100%) diagnostic test that could be used to refer patients to quarantine in the case of limited availability of genetic or serological tests is proposed.
