The Incubation Period of Coronavirus Disease 2019 (COVID-19) in Petaling District, Malaysia

introduction Globally, over 2 million population have been affected by the COVID-19 outbreak and over five thousand in Malaysia, with almost 100 deaths as of 22 April 2020. Knowledge on the incubation period (IP) of COVID-19 is scarce due to the novelty of the virus. The aim of this study was to determine the IP of COVID-19 infection in the district of Petaling, Selangor, Malaysia.

Materials and Methods A cross-sectional study was conducted between 3 February 2020 and 13 April 2020 by using secondary data from the Petaling District Health Office. The IP was classified as the time elapsed between exposure to a confirmed case and the date of onset of symptoms. The Kruskal-Wallis test was performed to compare the differences of IP between the groups.

Results A total of 219 cases were included in this study. Four main clusters were identified; corporate (n=44, 20·1%), religious (n=43, 19·6%), imported (n=74, 33·8%) and others (n=58, 26·5%). The median IP of COVID-19 among the cases was 5·0 days (interquartile range 3·0-8·0). The longest median IP was found in religious cluster (8·0 days, IQR 4·0-11·0), while the shortest median was corporate cluster (3·5 days, IQR 3·0-6·8). Significant difference was observed between corporate and religious clusters (p=0·001) (Table 1).

Discussion / Conclusion The median IP of COVID-19 of 5 days is within the range of IP estimated by the World Health Organization. A higher infecting dose as well as higher virulence of the strain could possibly lead to a shorter IP. Based on the longest median incubation period in our study (cluster religious), medical observation or quarantine period should be of a minimum of 8 days to halt the spread of disease. Therefore, our recommendation is to maintain current practice of quarantine of 14 days which will suffice to curb the spread of disease.