New omicron sublineages, discovered by South African scientists earlier this month, account for about 70% of new coronavirus cases in South Africa and the strains appear to be more infectious than predecessors.

The BA.4 and BA.5 sublineages appear to be more infectious than the earlier BA.2 lineage, which itself was more infectious than the original omicron variant, Tulio de Oliveira, who runs gene sequencing institutes in the country, said on Twitter.

A rapid increase in infections in the last 2 weeks was due to BA.4 and BA.5. Albeit coming from a low number. The 6,000 infections yesterday are underestimated as the test positivity ratio is around 20%. South Africa did not have a BA.2 Omicron wave-like Europe but only a large BA.1 wave. pic.twitter.com/8b4PZe6CkW

— Tulio de Oliveira (@Tuliodna) April 28, 2022

“Our main scenario for Omicron BA.4 and BA.5 is that it increases infections but that does not translate into large hospitalizations and deaths,” he said in a series of Tweets.

South Africa yesterday recorded 6,372 new cases with a positivity rate of 21.1%. That compares with 581 cases and a positivity rate of 4.5% on March 28. The National Institute of Communicable Diseases has said hospitalizations and deaths are rising, albeit slowly.