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May 5, 2022

Covid-19 cases are spiking in South Africa, and public health experts in the United States are following the data closely, waiting to see what it might reveal about how immunity from previous infections behaves over time.

South Africa has been a bellwether before. Scientists there were the first to discover the Omicron variant of the coronavirus late last year, setting off a global chain reaction. After a pandemic peak in December, cases in the country declined, but now they're on the rise again -- along with positivity rates and hospitalizations.

It could spell South Africa's fifth wave.

The spike has been tied to two new sublineages of Omicron, BA.4 and BA.5, which the World Health Organization added to its monitoring list last month. They're dominating transmission in the country, accounting for almost 60% of all new Covid-19 cases by the end of April, according to South Africa's National Institute of Communicable Diseases.
South African scientists have found that BA.4 and BA.5 can evade antibodies from previous infection well enough to spark a new wave, but are less likely to do so in people vaccinated against Covid-19. Almost all South Africans are either vaccinated or have had a previous infection.
Tulio de Oliveira, director of South Africa's Centre for Epidemic Response and Innovation, said that the research shows how the virus is changing as global immunity grows.

The Covid virus is evolving
"It looks that #COVID19 may be evolving differently and that we may not need a new variant to cause a new wave of infection. We are seeing this with BA.4 and 5 in SA and with BA.2.12.1 on the east coast of the USA," de Oliveira said in a series of Twitter posts.

"We are all tired of this virus, but he may not be tired of us. We need now to take seriously the decreasing immunity from previous infections," he added, explaining that vaccination is a much more reliable way to maintain immunity than infection.
These new Omicron subvariants are spreading around the globe. BA.4 sequences have been reported in 15 countries and 10 US states, while BA.5 has been detected in 13 countries and five US states, according to the website Outbreak.info, which is maintained by a coalition of academic research centers and supported by funding from the National Institutes of Health. BA.4 and BA.5 also have a growth advantage over Omicron subvariant BA.2, the dominant strain in the US, known as "stealth Omicron."

Deborah Birx, a former coordinator for the White House's coronavirus task force, said on Sunday that the US should be prepared for another possible coronavirus surge given the situation in South Africa and how it has served as a harbinger in the past.

"They're on an upslope again," Birx told CBS's "Face the Nation."

"Each of these surges are about four to six months apart. That tells me that natural immunity wanes enough in the general population after four to six months that a significant surge is going to occur again. And this is what we have to be prepared for in this country," she said, warning of another spike this summer across the US south.

Birx's warning comes as US cases are again on the rise. Nearly 60% of adults and 75% of children have antibodies indicating that they've been infected with Covid-19, according to new data from the US Centers for Disease Control and Prevention.

It is unclear what that means for protection against future infections, health experts say, and for that reason, the CDC says it is still important to stay up to date on Covid-19 vaccinations and boosters.

Covid-19 data reporting is becoming less frequent. Why is that a problem?
Many countries and US states are scaling back on how often they report key Covid-19 statistics, a shift that some experts worry might make it harder to track trends -- hindering efforts to mitigate outbreaks and curtail the negative effects of the virus.

Knowing specifically when cases happened and reporting the data frequently "equipped leaders to act quickly and save lives," Beth Blauer, executive director of the Centers for Civic Impact at Johns Hopkins University, wrote in a recent blog post.

"A possible seven-day lag for noticing changes in disease trends" when reporting shifts from daily to weekly could be "incredibly detrimental during a crisis, limiting the government's ability to intervene and protect people," Blauer wrote.

A year ago, all 50 states were reporting new Covid-19 cases on a daily basis. But that has gradually trailed off. Now, just six states are still reporting daily numbers.