The World Health Organization (WHO) are monitoring two new Omicron sub-variants to assess whether they are more infectious or dangerous.
According to the WHO, a handful of cases have been discovered of the BA.4 and BA.5 sub-variants, "in a few countries".
Both the new variants have additional mutations which the WHO said they are monitoring to see what potential "immune escape characteristics" they have.
"WHO is working with scientists to further assess the characteristics of these lineages and their public health implications," the organisation said in their weekly briefing update on Thursday.
Viruses mutate often but only some mutations affect their ability to spread or evade prior immunity from vaccination or infection, or the severity of disease they cause.
For example, BA.2 now represents nearly 94% of all genome-sequenced cases and is more transmissible than other sub-variants, but the evidence so far suggests it is no more likely to cause severe disease.
Cases of the BA.3 sub-variant have been detected but appear not to be making any headway against BA.2.
However, Director-General of the WHO Dr Tedros Adhanom Ghebreyesus said the virus remained deadly.
"This virus has over time become more transmissible and it remains deadly especially for the unprotected and unvaccinated that don’t have access to health care and antivirals," he said.
The WHO are also monitoring another variant, XE, that is a "recombination" of Omicron's BA.1 and BA.2 variants, meaning the two have merged.
It is believed to be 10% more transmissible than the BA.2 variant and was first detected in the UK in January.
Over 1000 cases have been reported in the UK, while it has also been detected in the US, Japan, India, Thailand and Israel.
New Zealand recorded 9563 new Covid-19 cases on Thursday. There are 528 people in hospital with the virus, including 28 in an intensive care or high dependency unit.
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