You are presented with a paragraph from a COVID-19 literature. Classify the topics of this piece of text by choosing from the following categories:

- Epidemic Forecasting: The content relates to predictions about the spread of COVID-19.
- Treatment: The paragraph discusses therapeutic methods or medication for COVID-19.
- Prevention: The content covers measures to prevent the spread of COVID-19.
- Mechanism: The paragraph explains the biological mechanisms of the virus.
- Case Report: The content is a report of a COVID-19 case.
- Transmission: The paragraph discusses how COVID-19 is transmitted.
- Diagnosis: The content is about diagnosing COVID-19 in individuals.

Your classification should be provided as an element within a JSON array. The array should be formatted with topics enclosed in double quotes and separated by commas, following the JSON format, for example: ["Topic1", "Topic2", ...]. Include all applicable topics within the array. Your output should be a valid JSON array, and no additional text should be included in your response.

Article:

During the Coronavirus disease 2019 (COVID-19), a general decrease in the presentations to emergency departments (ED) was reported. However, we suspect that there was a lower number but an unchanged pattern of ED visits for urgent conditions in 2020 compared to 2019. This retrospective study assessed the change in the number of presentations in the ED of a tertiary level university hospital in Milano (Lombardia, Italy). Compared to 2019, a significant drop in ED presentations occurred (-46.4%), and we recorded a -15.7% difference in the proportion of patients admitted with white codes. The pattern of hourly presentations to the ED was unchanged, with overcrowding during the working daytime. COVID-19 changed ED flows, likely causing an overall reduction in the number of deferrable conditions. However, the pattern associated with urgent conditions did not change abruptly in 2020.
["Prevention"]