The first case of Omicron's highly transmissible and immune-evasive descendant called BQ.1 has been detected in Thailand, according to the Centre for Medical Genomics at Ramathibodi Hospital.
The centre cited information from the Global Initiative on Sharing Avian Influenza Data (Gisaid), an international genomic database.
The centre posted on Facebook that the US Centers for Disease Control and Prevention (CDC) has issued an alert for the outbreak of BQ.1 and BQ.1.1, the two descendants of Omicron's BA.5 sub-variant.
In particular, BQ.1 now makes up one in 10 cases in the US, according to the CDC.
The Centre for Medical Genomics posted that Dr Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases, said BQ.1 and BQ.1.1 have dangerous qualities or characteristics that could evade some of the available interventions.
He said the new strains are "pretty troublesome" and they have a concerning "doubling time", referring to how quickly they spread.
BQ.1 and BQ.1.1 are reported to be resistant to current antibody medications used to treat Covid-19 patients, such as Evusheld and Bebtelovimab, said the Centre for Medical Genomics.
Second-generation vaccines may be needed to trigger better antibodies against an increase in the viral load from the BQ.1 and BQ.1.1 sub-variants.
A second generation of antibody cocktail medications may also be required to treat those infected with these new sub-variants, the centre said.
BQ.1 can also dodge the protective antibodies from prior infection or those created by vaccination, according to the centre.
People who received vaccines against the BA.5 sub-variant may still have a slightly higher level of antibodies against BQ.1 given that it is a descendent of BA.5, it said.
BQ.1 spreads 15% faster than BA.5.2 and 14% faster than BA.2 on a daily basis. In light of this, BQ.1 is expected to overtake BA.5 as the dominant strain by the end of this year or next year, according to the Centre for Medical Genomics.
However, there is no clinical proof that BQ.1 and BQ.1.1 will cause more severe infections and more fatalities than previous sub-variants, the centre said.
Previously, two cases of XBB sub-lineage were detected last month in two people: a foreign woman, 60, who arrived from Hong Kong and a Thai woman, 49, who returned from Singapore, according to the Department of Medical Science.
Both of the women had an examination at the same hospital where they tested positive.
They experienced mild symptoms and have already recovered.
