KUALA LUMPUR: The World Health Organisation (WHO) has issued a warning against a new mutant 'XE' variant of Omicron that could be more transmissible than strains of Covid-19 seen before.
XE is a a recombinant strain, a mutant hybrid of Omicron BA.1 and BA.2 sublineages of Covid-19.
In its Covid-19 Weekly Epidemiological Update (published on March 29), the WHO said the XE recombinant (BA.1-BA.2) was first detected in the United Kingdom (UK) on Jan 19 and over 600 sequences have been reported and confirmed since.
"Early-day estimates indicate a community growth rate advantage of ~10 per cent as compared to BA.2, however this finding requires further confirmation.
"XE belongs to the Omicron variant until significant differences in transmission and disease characteristics, including severity, may be reported.
"WHO continues to closely monitor and assess the public health risk associated with recombinant variants, alongside other SARS-CoV-2 variants, and will provide updates as further evidence becomes available," the report read.
According to the Bangkok Post, Thailand has recorded its first case of the Omicron XE on Saturday (April 2) found through genomic sequencing of a swab sample taken from a Thai patient at the Center for Medical Genomics, Ramathibodi Hospital.
The WHO had earlier in its weekly update dated March 22 noted that recombination of variants of the same virus is a natural phenomenon and can be regarded as an expected mutational event.
WHO, it said has been notified of several recombinant variants, either recombination between Delta and BA.1 variants, or BA.1 and BA.2 variants.
Two other hybrid or recombinant viruses have been identified thus far - XD and XF, which are a combination of Delta and Omicron variants.
"The same monitoring and assessment process is applied to these recombinants as for any other emerging variant, after verification and exclusion of potential contamination or co-infection.
"Two Delta and Omicron recombinants and one BA.1 x BA.2 recombinant have now been given Pango lineage designations XD, XE and XF.
"None of the preliminary available evidence indicates that these recombinant variants are associated with higher transmissibility or more severe outcomes," it wrote.
The UK has reported 637 cases of XE and experts saying it has shown a variable growth rate.
According to the UK Health Security Agency (UKHSCA), XE showed evidence of community transmission within England, although it is currently less >1 per cent of total sequenced cases.
Early growth rates for XE, it said were not significantly different from BA.2, but using the most recent data up to March 16, the agency said XE has a growth rate 9.8 per cent above that of BA.2.
However, it cautioned that "as this estimates has not remained consistent as new data have been added, it cannot yet be interpreted as an estimate of growth advantage for the recombinant.
"Numbers were too small for the XE recombinant to be analysed by the region," the agency said in its Covid-19 technical briefing 39 report (published on March 25).