Study: Incubation period decreases with each COVID-19 variant

Editor's Note 

New research in China, led by Min Liu of the Department of Epidemiology and Biostatistics at Peking University's School of Public Health in Beijing, shows that the incubation period is significantly shorter when people are infected with COVID-19 now than at the beginning of the pandemic, US News & World Report August 23 reports.

The researchers examined data on incubation periods from various studies conducted throughout the pandemic, comprising more than 8,100 patients infected with COVID-19. They explained that "identifying the incubation period of different variants is a key factor in determining the isolation period" for individuals testing positive for COVID-19.

According to the Chinese team, the findings indicate that, on average, the incubation periods for each COVID-19 variant were:

• 5 days for the Alpha variant
• 4.5 days for the Beta variant
• 4.4 days for the Delta variant
• 3.4 days for the Omicron variant.

The researchers cautioned, however, that the above figures are averages, and that a wide range has been reported; the shortest mean incubation reported was 1.8 days and the longest incubation was 18.87 days, according to the research.

"At present, some countries around the world require close contacts to be isolated for 14 days," Liu's group said. "However, with the shortening of the incubation period of new variants, the isolation period can be adjusted appropriately to reduce the pressure on the health system."

The findings were published on August 22 by JAMA Network and can be accessed here.