Background: Coronavirus disease 19 (COVID-19) started as pneumonia of unknown cause detected first in China, in December 2019 and rapidly spread as a pandemic. The most common symptoms of COVID-19 are fever, dry cough, breathing difficulty and tiredness, and the median incubation period is about 5 days. The present study was done to estimate the median incubation period of COVID-19 cases admitted in a tertiary care center in north Kerala.

Methods: This cross-sectional study included 40 COVID-19 cases admitted in a tertiary care center during three months study period. The incubation period is the period between date of exposure and date of symptom onset. In the case of patients with travel history, the date of arrival in Kerala was considered as date of exposure and for primary contacts, the date of last contact with COVID case was considered as date of exposure.

Results: The median incubation period of COVID-19 was estimated to be 4 days (interquartile range 7). It was also found that females, those persons with comorbidities and those who got infected by local transmission had a longer mean incubation period compared to males, those without comorbidities and imported cases, respectively.

Conclusion: The median incubation period of COVID-19 was estimated to be 4 days. Factors like presence of comorbidities, gender, type of transmission were found to affect incubation period, but more studies are needed to have a thorough understanding.

Keywords: COVID-19, Incubation period, India, Kerala