COVID-19 Incubation Period: An Update

摘要

Median and maximum incubation periods are estimated from patients connected to the disease-origin province in China. Infection with SARS-CoV-2, the virus that causes COVID-19, appears to be highly contagious and is primarily spread by droplets. Containment efforts have emphasized quarantine during the incubation period as the most effective measure to limit spread. Because of the personal and economic toll of this measure and its implication for transmission, we need to maximize our understanding of the incubation period. These authors studied the case records of 181 patients (median age, 44.5 years; 60% male) who had visited Wuhan, the city in China where the infection was first identified (161 cases), or been in contact with an infected person before becoming symptomatic and testing positive for COVID-19 between January 4 and February 24,2020. The investigators classified risk for undetected symptomatic infection as low (1 in 10,000), medium (1 in 1000), or high (1 in 100) and considered monitoring programs of varying length. In the resulting models, estimated median incubation time (IT) of COVID-19 was 5.1 days; mean IT was 5.5 days. For 97.5% of infected persons, symptoms appear by 11.5 days. Fewer than 2.5% are symptomatic within 2.2 days. Estimated median IT to fever was 5.7 days. Among 108 patients diagnosed outside mainland China, median IT was 5.5 days; the 73 patients diagnosed inside China had a median IT of 4.8 days. Using exposures designated as high risk and a 7-day monitoring period, the estimate for missed cases was 21.2 per 10,000. After 14 days, the estimated number of missed high-risk cases was 1 per 10,000 patients.