Omicron – the most contagious virus in history?
The new variant conquered the planet in less than a month.
A comparison between measles – until now a candidate with strong claims to being the most infectious disease – and Omicron is instructive.
According to Roby Bhattacharyya, an expert in infectious diseases at Massachusetts General Hospital, one person with measles infects another 15 on average in the absence of vaccination, compared to the six infected by Omicron.
The key, however, is in the so-called generation time: the days that elapse from when the first person is infectious until those infected by it are also infectious.
About 12 days go by with measles. In the case of Omicron, it only takes four or five days.
It is explosive.
“A case of measles would give rise to 15 cases within 12 days. A case of Omicron would originate another six at four days, 36 cases at eight days and 216 at 12 days,” Bhattacharyya told the Spanish daily El País.
In 35 days there would be 280,000 Omicron cases and 2,700 of measles in the absence of vaccines.
Medical historian Anton Erkoreka told El País that Omicron “is the most explosive virus with the most rapid diffusion in history”.
The black plague of the sixteenth century and cholera in the nineteenth century (both bacterial infections) took years to expand globally. The original COVID variant detected in 2019 took three months to cross the planet.
“The Omicron variant has beaten that record of expansion,” said Erkoreka.