After XBB.1.5, also known as “Kraken”, became the dominant strain of Covid-19 in the United States of America (US), accounting for about 61% of cases, according to health data authorities, there is now a new concern: CH.1.1, nicknamed ‘Orthrus’.
The US Centers for Disease Control and Prevention is testing this new strain of the Omicron variant with a Delta mutation, as it is estimated to have caused 1,5% of cases in the US, Fortune magazine reveals. The name “Orthros”, associated with the mythical two-headed dog of Hercules, was assigned to by Australian camouflage tracker Mike Honey.
While not much is known about the relatively new strain, levels of which have been rising worldwide since November, like other variants, it has the potential to be more contagious, evade immunity from vaccines and infections, and cause more serious illness.
Additionally, it has a disturbing mutation in common with the Delta variant that could make it dangerous. Although CH.1.1 is not a ‘Deltacron’ – a combination of Delta and Omicron – it is an excellent example of convergent evolution, a process in which variants of the coronavirus evolve independently but receive the same mutations.
Where and when was it discovered?
CH.1.1 emerged in Southeast Asia this fall and is now responsible for more than a quarter of infections in parts of the UK and New Zealand, according to a preprint paper released last week by researchers at State University. from Ohio, USA .
It has spread rapidly since November and now comprises about 10% of daily Covid-19 samples worldwide, according to outbreak.info, and is therefore being monitored by the World Health Organization (WHO), the international organization said in a report shared on Wednesday.
In which countries was it detected?
New Zealand is currently the country with the most CH.1.1 cases, accounting for more than a third of all cases. Hong Kong and Papua New Guinea also stand out on this list, accounting for about a quarter of the cases in each country, followed by Cambodia and Ireland, with just under a fifth of all cases.
Why is it so worrying?
Although XBB.1.5 remains the most contagious strain of Covid-19 so far, according to a January 19 report by variant tracer Cornelius Romer, CH.1.1, like XBB.1.5, is highly contagious, with levels doubling every two weeks or so.
This strain has the ability to infiltrate where the coronavirus infects human cells, the Ohio State researchers warned, meaning it has the potential to override, even partially, antibody immunity against prior infection and vaccination, as and cause more serious diseases.
How did it evolve?
CH.1.1 is a descendant of BA.2.75, a variant that was named ‘Centaur’ this summer but was eventually scrapped. Currently, most of the dominant strains are descendants of either BA.5, which toured the world this summer, or BA.2.75, the stress-specialized “family” variant.
In case it was recently exposed to a BA.5 variant, it may be less vulnerable to new BA.5 variants for a while, however it is more vulnerable to BA.2.75 variants and vice versa. Note that XBB.1.5 is also a descendant of BA.2.75.
Does vaccination protect against this strain?
The protection offered by the original SARS-CoV-2 vaccine is waning, Ohio State researchers warned when recommending booster vaccination. However, they noted that available vaccines offer less protection against CH.1.1 and CA.3.1 than against other variants such as XBB and BQ.1.1.