The number of coronavirus cases is on the rise again in South Africa and public health experts are monitoring the situation and are eager to know what is causing the spike, what it says about immunity against previous infections and what its implications are worldwide.
South Africa experienced a decline in cases after reaching an Omicron-fueled pandemic peak in December. But in the past week, cases have tripled, positivity rates have risen and hospitalizations have also increased, health officials said. The wave will confront the country with a possible fifth wave.
The peak is linked to BA.4 and BA.5, two subvariants that are part of the Omicron family.
Tulio de Oliveira, director of the KwaZulu-Natal Research and Innovation Sequencing Platform in South Africa, said BA.4 and BA.5 show how the virus develops differently as global immunity increases. Variants have sprung up “out of nowhere” in recent years, said Mr. de Oliveira.
“What we’re seeing now, or at least the early signs, aren’t entirely new variants emerging, but current variants are starting to create lines of their own,” said Dr. de Oliveira. Since first identification in South Africa and Botswana last November, Omicron has produced several sub-variants.
Some scientists are trying to understand what the peaks of BA.4 and BA.5 in South Africa, which are mainly concentrated in the provinces of Gauteng, Western Cape and KwaZulu-Natal, say about immunity to previous Omicron infections. The highly contagious Omicron variant first appeared in South Africa late last year and then quickly spread around the world.
In South Africa, researchers estimate that about 90 percent of the population has some immunity, partly from inoculation but largely from previous infection. Still, immunity to infection usually begins to wane after about three months. It’s normal to see reinfection at this stage, said Dr. Ali Mokdad, an epidemiologist at the University of Washington, and formerly of the Centers for Disease Control and Prevention.
Emerging data show that BA.4 and BA.5 evade the natural defenses produced by infection with the original Omicron variant, known as BA.1, in unvaccinated humans, reducing the number of cases in South Africa in recent years. winter skyrocketed, said Dr. de Oliveira. † The result is symptomatic infections with the new subvariants.
“That’s why it’s starting to fuel a wave in South Africa,” said Dr. de Oliveira.
Scientists are still studying whether this new wave causes milder or more serious diseases, and it’s unclear whether the two subvariants could show up elsewhere in the world.
“We’re at a global moment where the past can’t really predict the future,” said Dr. Kavita Patel, a primary care physician who led the pandemic preparedness for the H1N1 swine flu virus during the Obama administration.
The familiar patterns — one wave in one country means another wave elsewhere — no longer necessarily work like clockwork, said Dr. patella. But monitoring situations and data from countries like South Africa provides reliable signals to understand the evolution of the virus.
Currently, another Omicron subvariant, BA.2, is dominant in the United States, and BA.2.12.1 is also gaining momentum, although public health officials have determined that BA.4 and BA.5 are circulating at low levels.
Whatever the dominant variant, “the lesson here is that stopping the transmission is the most important,” said Dr. Eric Feigl-Ding, an epidemiologist who heads the Covid-19 task force at the World Health Network.