Omicron’s latest subvariants may have evolved to target the lung, causing fears that Covid’s next wave might begin.
New NHS data shows that hospital admissions for patients with Covid in England have begun to grow again.
The World Health Organization has been investigating two Omicron subvariants since April to assess whether they are more infectious or dangerous than their predecessor. Both BA.4 and BA.5 have been added to the agency’s watch list.
Last week, new figures showed that Covid-19 infections in the UK rose 43 per cent the week after the platinum jubilee celebrations, and the two new subvariants are believed to be behind the sudden rise .
In addition, around 1.4 million people in the UK had coronavirus in the week ending June 11, compared to about 990,000 the previous week.
According to preliminary data from Kei Sato of the University of Tokyo and colleagues, BA.4, BA.5 and BA.2.12.1 may have evolved to promote infection of lung cells, rather than tissue. the upper respiratory tract, making them more similar to the earlier variants, such as Alpha or Delta.
The propensity of earlier variants of Omicron to prefer to infect non-lung tissue may be one of the reasons why infections are usually milder in most people.
“Overall, our research suggests that the risk of [these] Omicron variants, especially BA.4 and BA.5, for overall health are potentially larger than the original BA.2, ”Sato said.
Professor Sato’s experiments indicate that BA.4, BA.5, and BA.2.12.1 replicate more efficiently in human lung cells than BA.2, while other hamster experiments suggest that BA.4 and BA.5 can cause more serious illnesses.
“It looks like these things are returning to the most dangerous form of infection, so they go down to the lungs,” said Dr Stephen Griffin, a virologist at the University of Leeds.
Total infections have now returned to levels last seen in early May, but remain well below the record 4.9 million at the peak of the Omicron BA.2 wave in late March. Covid’s hospital admissions are also below the levels recorded during the previous wave.
The ONS said the latest increase was “probably caused by infections compatible with Omicron variants BA.4 and BA.5”, which are now believed to be the most dominant variants in much of the UK.
Professor Christina Pagel, director of the Operational Clinical Research Unit at University College London, has echoed this.
“While the jubilee celebrations would certainly not have helped,” he said, “the current wave is precipitated mainly by BA.4 / BA.5 and BA.2.12.1 becoming dominant and driving a new rise, probably due to a greater ability to escape the immunity of previous infections and vaccines “.
Dr Mary Ramsay, of the UK Health Safety Agency, said: “It is encouraging that we are not seeing an increase in admissions to intensive care units, but we are closely monitoring the data and assessing the possible impact of the subvariants BA.4 and BA.5.
“As we enter the summer, it’s still important to remember that Covid-19 hasn’t gone away and get vaccinated to reduce the risk of getting seriously ill with the virus.”