incubation period of COVID-19

A number of serious pneumonia cases started to frequently appear in Wuhan, China in December 2019. The number of pneumonia cases was puzzling until the identification of the cause; the novel human coronavirus disease (COVID-19). January 30th, 2020 marked 80,000 reported positive cases around the globe. When it comes to COVID-19, there are still epidemiological features that are being researched, such as the incubation period of the virus.

Other strains of coronavirus such as severe acute respiratory syndrome (SARS) and Middle East Respiratory Syndrome (MERS) have incubation periods similar to what researchers have already estimated about COVID-19. The median incubation period of SARS is five days, with a range of up to two-to-fourteen days. The median incubation period of MERS is five-to-seven days, with a range of two-to-fourteen days.

A study published in the Annals of Internal Medicine focused on helping to expand information on, and develop a well-defined estimation and understanding of the incubation period of COVID-19. The study also focused on active monitoring, the process in which persons that may have been, or have been exposed to the disease, report their health conditions daily to their local health organizations. A better understanding of the amount of time needed for active monitoring will help to avoid missed diagnoses.

Results were obtained by assessing news and health report data pertaining to positive COVID-19 cases between January 4th, 2020 and February 24th, 2020. Researchers specifically assessed reports in locations without local COVID-19 spread. There was no data included in this study that involved asymptomatic cases. Factors that were looked at were onsets of fever or other symptoms, and exact timelines, if there were any.

Researchers used data from 181 positive COVID-19 cases. Some cases occurred in Mainland China (25), while others occurred in areas outside of Mainland China (24), but all were outside of the province of Hubei. A majority of infected persons recently travelled to Wuhan or had recently resided there. Other infected persons had come into contact with those who had been to Hubei or had been around persons who had tested positive for COVID-19.

Researchers concluded an estimated median incubation period of 5.1 days. They estimated that 97.5% of patients develop symptoms after eleven and a half days. This established that with proper active monitoring or quarantine, 101 out of 10,000 persons develop symptoms after two weeks (fourteen days). Forty-four and a half was the median age of all assessed cases, and there were more infected males (60%) than there were female (38%). Patients were typically hospitalised 1.2 days after the onset of symptoms.

These estimations help the healthcare community, as well as the public, gain a better understanding of the incubation period of COVID-19. However, further research is needed in the fight against this new virus.

Written by Laura Laroche, HBASc, Medical Writer

References: Lauer, Stephen A. et al. “The Incubation Period of Coronavirus Disease 2019 (COVID-19) From Publicly Reported Confirmed Cases: Estimation and Application”. Annals of Internal Medicine. March 10th, 2020. Online.

Image by Pete Linforth from Pixabay 

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