Characteristics and courses of COVID-19 in patients from the first through fifth waves of the disease: Focused on a single public health center in Tokyo, Japan

Abstract

Objective Coronavirus disease 2019 (COVID-19) became a global public health threat, and local public health centers in Japan implemented an infectious disease response to support patients. The response was subsequently modified to meet the needs for each of the five waves of infection. The study aim was to analyze the characteristics and courses of the disease in patients with COVID-19 at a single public health center. The study period included the first through fifth waves of the disease.Methods We utilized a descriptive epidemiological design in this study and data of patients with COVID-19 from one administrative district in Tokyo, Japan. We analyzed age, gender, nationality, symptoms at diagnosis, the route of infection, the recovery environment, and associated morbidity intervals, including case fatality rate, days from symptom onset to diagnosis, days from diagnosis to hospitalization, and recovery time for each of the first through fifth waves.Results From February 2020 to November 2021, 11,252 patients were diagnosed with COVID-19. Specifically, in the first wave, 151 patients were diagnosed, followed by 803 in the second wave, 2,406 in the third wave, 1,480 in the fourth wave, and 6,412 in the fifth wave. Hospitalization was the primary recovery environment during the first wave, while home recovery became the primary approach from the third wave onward. The case fatality rate was highest during the first wave, likely because of limited testing and treatment options for severe cases. The median time from onset to diagnosis was seven days in the first wave, significantly longer than for the other waves. The median time from diagnosis to hospitalization was one day in the first through fourth waves but three days in the fifth wave. The extension of this interval suggests that hospitalization was delayed in this wave as the number of severe patients increased rapidly, likely because of the novel COVID-19 variant.Conclusion This study of patients testing positive for COVID-19 provides valuable insights into the characteristics and courses of the pandemic within this district. These findings can inform regarding the development of effective strategies to manage the ongoing COVID-19 pandemic and other future emerging infectious diseases.