There were 4282 daily Covid-19 cases reported today, breaking a plateau that has lasted about three weeks.

The number is 9.4 per cent higher than the previous Tuesday, usually the highest day of the week because it captured some slow weekend reporting.

The last time cases were in the 4000s was August 17, as the country came down from the major winter wave.

Cases began to increase again in mid-October, before hitting the plateau.

The Ministry of Health says it expects the current infection wave to keep rising but could not accurately predict when that will happen and how big it will be.

Experts have said that's because it's unclear how the several new variants will play out, and what the impact of immunity from previous infections will be.

It says BQ 1.1 is increasing faster than the previous dominant variant BA.5 and the new arrival XBB is showing some evidence of being able to evade people's immunity but more evidence is needed.

Wastewater testing suggests about three quarters of all cases are being reported.

-Rowan Quinn/RNZ.