Data is emerging from Gauteng, where the Omicron COVID strain first surfaced, which is giving experts cause for concern.
According to figures from the South African province, the BA.2 form of the variant has replaced the original BA.1 strain at a fairly rapid pace.
Epidemiologist and senior fellow with the American Federation of Scientists Eric Feigl-Ding says the data is "not a good signal".
While there is no evidence that this subvariant causes more severe illness that BA.1, there are growing indications that it is significantly more transmissible.
He points to a new study from Denmark that indicates BA.2 is one and a half times more contagious than BA.1.
But perhaps the biggest source of experts' fears is that its potential to cause reinfection relatively quickly could prolong the pandemic.