Study: Covid-19 Has Evolved


According a study out of Beijing University and published recently on the Journal of the American Medical Association the novel Coronavirus (Covid-19) has evolved becoming more transmissible and virulent and with shortened its incubation period.

The key finding of the study based on review and meta-analysis of 141 articles showed a pooled incubation period of 6.57. “The incubation periods of COVID-19 caused by the Alpha, Beta, Delta, and Omicron variants were 5.00, 4.50, 4.41, and 3.42 days, respectively”.

Reporting first about the study, Fortune writes “The initial ‘wild type‘ strain of COVID detected in Wuhan, China, in late 2019 had an incubation period of around 5.2 days. COVID’s Alpha variant—which burst onto the scene in the U.K. in December 2020—took about five days for symptoms to develop after exposure.”

“By the time the Beta variant was discovered a short time later, the incubation period had shortened to 4.5 days. The Delta variant saw an incubation period of 4.41 days, and Omicron’s incubation period is currently 3.42 days,” Fortune adds referring the study.

The study authors wrote “Some countries around the world require close contacts to be isolated for 14 days. 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.”

In the study conclusions, the authors write:

Although variants such as Alpha, Beta, and Gamma are currently only prevalent in a few countries in Southeast Asia, South America, and Africa, the Delta and Omicron variants have become the dominant strains in many countries around the world. Identifying the incubation period of different variants is a key factor in determining the isolation period. The pooled incubation period of COVID-19 in this study was 6.57 days. The incubation period for COVID-19 caused by the Alpha and Beta variants was approximately 5 days. The incubation period of COVID-19 caused by the Delta and Omicron variants was significantly shorter than that of the other variants.

The study result suggested that “with the evolution of mutant strains, the incubation period of COVID-19 decreased gradually from Alpha variant to Omicron variant”.