SA scientists are closely monitoring a rapid rise in new coronavirus infections, which have more than doubled in the past week, but say it is too soon to tell whether there will be a similar upswing in hospital admissions.
“At this point there are no warning bells about severity. But the big caveat is it is still early days,” said University of KwaZulu-Natal epidemiologist Salim Abdool Karim, who was previously the government’s top coronavirus adviser. “There is a high level of uncertainty,” he said.
The sharp rise in new cases could have been triggered by increased social interaction over Easter, Passover and Ramadan, which fell simultaneously this year, as much as the emergence of the new Omicron lineages BA.4 and BA.5, said Karim. Whether the increase was the start of a rapid fifth wave of coronavirus infections would likely be clear in about a week’s time, he said.
The national seven-day moving average of new recorded cases had by Sunday risen to 3,097, a week-on-week increase of 137%, according to Council for Scientific and Industrial Research senior researcher Ridhwaan Suliman. The lion’s share of the new cases have been recorded in Gauteng, where the seven-day moving average of new cases rose 135% week on week to 1,542, he said.
The fact that the daily case incidence had breached the five per 100,000 population threshold, and that the test positivity rate was consistently above 10% (it stood at 16.7% on Sunday) suggested the increase was likely to be sustained, said Suliman.
Wits vaccinologist Shabir Madhi said SA was on the cusp of a resurgence of Covid-19, likely driven by the Omicron lineage BA.4. Given that more than 80% of the population had some immunity to the virus, from prior infection or vaccination or a combination of the two, this was likely to cushion the impact of a fresh surge in cases and protect people from severe disease, he said on Twitter.
SA’s fourth wave, driven by earlier Omicron lineages, saw a decoupling of cases and hospital admissions, and the same pattern was likely in a fifth wave driven by BA4, he said.
“We need to be cautious but there is no need to panic as we live with the virus,” he said, urging the government to do more to ensure at least 90% of people over the age of 50 were vaccinated. About two thirds of people in this age group have been immunised.
The Omicron lineages BA.4 and BA.5 have rapidly displaced the older BA.2 lineage, according to surveillance data from the National Institute for Communicable Diseases (NICD).
In March BA.2 accounted for 80% of the genomes sequenced in SA, and BA.4 and BA.5 accounted for 11% and 3% respectively. By April 9 the proportion of BA.2 had fallen to 53%, while BA.4 and BA.5 rose to 28% and 16% respectively, according to the latest genomic surveillance report from the NICD.
“The genomic sequencing always lags a little, so we are always a bit cautious because we don’t have data that is right up to date. But we have a reasonably high level of confidence that the increasing cases are associated with these two lineages (BA.4 and BA.5), said University of KwaZulu-Natal infectious disease specialist Richard Lessells.
There were no signs yet of BA.4 and BA.5 causing more severe illness, but there was insufficient data to be sure, he said.
“Assessing the severity of the variants gets more and more complex as almost all of us have now some degree of immunity against severe disease (from prior infection or vaccination or both) and many of us have very strong immunity against severe disease. It thus becomes increasingly hard to understand the intrinsic virulence of the variant or the lineage,” Lessells said.
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