Trends in clinical features of novel coronavirus disease (COVID-19): A systematic review and meta-analysis of studies published from December 2019 to February 2020.

Background: Since novel coronavirus disease (COVID-19) emerged, various clinical features of COVID-19 have been reported.
Methods: We conducted a systematic review of published studies reporting the clinical features of COVID-19. Two investigators independently searched PubMed (December 2019-February 2020) for eligible articles. A meta-analysis was performed to measure the frequencies of clinical outcomes and symptoms of COVID-19. A stratified analysis was conducted according to the timeline of outbreak and exposure histories: Group I, most patients were exposed to the Hunan seafood wholesale market and lived in Wuhan, Hubei province; Group II, patients lived in Hubei province but were not directly exposed to the market; and Group III, patients lived outside Hubei.
Results: Thirteen studies, all from China, were eligible. The estimated mortality rate among all studies was 2.12%, but that in Group I was 8.66%. The incidence of acute respiratory distress syndrome in Group I was 20.00%. Both fever and cough were major symptoms, and their frequencies were higher in Group I than in Groups II and III, while the frequency of diarrhea in Group I was lower than that in Group III. The estimated frequency of dyspnea in Group I was 37.18%, while those in Groups II and III were 16.95% and 7.03%, respectively.
Conclusions: The trends in the clinical features of COVID-19 changed from December 2019 to February 2020. During this observation period, as the infection continued to spread, the clinical conditions for majority of patients became less severe with the changes in the route of transmission.
Competing Interests: Conflict of Interest The authors have no conflicts of interest to declare.
(Copyright © 2020 The Japanese Respiratory Society. Published by Elsevier B.V. All rights reserved.)