Study confirms coronavirus median incubation period at 5.1 days

By Angela Betsaida B. Laguipo, BSNMar 10 2020

Since the start of the novel coronavirus outbreak in late December 2019, doctors and health officials have imposed a quarantine period of 14 days since the estimated incubation period of the virus was expected to be between three and 14 days. A new study affirms that it may take about five days after exposure before patients manifest the symptoms of the disease.

The study, pioneered by scientists from Johns Hopkins Bloomberg School of Public Health, reveals that 5.1 days was the median length of time before people started showing signs of the disease. However, there is a wide range of incubation periods, with some people taking up to two weeks.

Understanding the coronavirus disease (COVID-19)’s incubation period is the key to control and contain its spread. This way, health officials may impose appropriate isolation and quarantine orders. Further, the current 14-days quarantined period is adequate to detect those who have contracted the viral disease.

Novel Coronavirus SARS-CoV-2 Transmission electron micrograph of a SARS-CoV-2 virus particle, isolated from a patient. Image captured and color-enhanced at the NIAID Integrated Research Facility (IRF) in Fort Detrick, Maryland. Credit: NIAID

Incubation Period

It is imperative to know the incubation period of infections since it is from there that health officials base their quarantine efforts. For instance, the U.S. Centers for Disease Control and Prevention (CDC) used the standard incubation period of two weeks during the current outbreak, which was based on a previous estimate by health experts. The new five-day incubation period is within the standard being implemented across the globe today.

The novel human coronavirus, now officially called severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was identified in China in December 2019. It originated at a seafood market in Wuhan City, Hubei province.

There was limited knowledge of many of the virus’s vital epidemiologic features, including its incubation period before developing into COVID-19 disease. Therefore, the team wanted to provide an estimate of the incubation period length and describe its public health implications. To arrive at their findings, the team utilized a pooled analysis of confirmed COVID-19 cases reported between Jan. 4 and Feb. 24, 2020, across news reports and press releases from 50 provinces, regions, and countries outside Hubei province.

They examined about 181 confirmed cases of COVID-19 and found that the median incubation period was 5.1 days. Further, the team concluded that an estimated 97.5 percent of the confirmed cases would develop the symptoms within 11.5 days. The results show that the current quarantine period duration is ample enough to observe persons under investigation for the coronavirus, validating the current policies of quarantine as the optimal time stretch for self-isolation after suspected exposure.

Also, under conservative assumptions, 101 of every 10,000 cases will develop symptoms after 14 days of active monitoring and quarantine, which still supports the current recommendations by the World Health Organization (WHO) and CDC.

“This work provides additional evidence for a median incubation period for COVID-19 of approximately five days, similar to SARS. Our results support current proposals for the length of quarantine or active monitoring of persons potentially exposed to SARS-CoV-2. However, longer monitoring periods might be justified in extreme cases,” the authors concluded in the study, which was published in the Annals of Internal Medicine.

Coronavirus global status

The coronavirus disease (COVID-19) outbreak has so far infected 113,808 people across the globe, and the death toll has now topped 4,000. Italy has the highest number of infections and deaths outside China, with 9,172 infections and 463 deaths. Iran comes in second with the 7,161 confirmed cases and 237 deaths.

Both South Korea and Iran have reported increasing local. Meanwhile, Spain has increasing deaths related to the coronavirus disease, with 30 deaths and 1,073 infections.