After the original Omicron variant appeared on US shores late last year and caused the deadliest wave of the pandemic, a series of Omicron sub-variants have come and gone: BA.1.1, BA.2, BA.2.12.1 and now BA. 4 and BA.5. The BA.5 was first spotted in South Africa on 26 February. Less than a month ago, on June 4, it accounted for only 9.6% of US cases, while its predecessor BA.2.12.1 was at the top of the heap at 62%. Today, the CDC estimates that the subvariable accounts for about 54% of new cases here. This is double BA.2.12.1, which now accounts for 27% of infections. The rise of BA.5 also leaves its sister sub-variable BA.4 at 16%. It’s a faster climb than any other variation during the pandemic. And there have been many of them. CDC One reason BA.5 is so dominant is that it appears to be more transmissible even than BA.2.12.1 — (BA.4 has some of the same key spike protein mutations as BA.5, but it didn’t have the same impact. “The Omicron BA.5 subvariant is the worst version of the virus we’ve seen,” Eric Topal, who is founder and director of the Scripps Research Translational Institute, Professor of Molecular Medicine and Executive Vice President of Scripps Research, said in a post on last week. “It takes immune evasion, already extensive, to the next level and, as a function of that, improved transmissibility, well beyond Omicron (BA.1) and other variants of the Omicron family that we’ve seen.” In other words, BA.5 is much better at avoiding immunity provided by vaccines and especially good at avoiding immunity that has arisen from previous infection. For example, BA.4 and BA.5 caused a significant increase in South Africa recently, which was not affected by the county’s high level of immunity. According to the journal Nature, those with “hybrid immunity” from vaccination and a previous infection are less able to fend off BA.4 or BA.5 than they were earlier strains. This is because the vaccines we have now target the spike proteins of earlier strains. And the new variants have some very different mutations. While vaccines are less effective, they are and still are more effective than immunization through infection. The jabs also help those infected with BA.4 and BA.5 better prevent the more unpleasant effects of the virus. While cases have remained fairly static in the US, the New York Times notes that this may be more a result of counting than actual counting. The paper reports that with local and federal cuts to testing services, “laboratory-based PCR testing capacity in July will be only half of what it was in March.” Add to that the increased use of home tests, the results of which generally go unreported, and virus surveillance across the country is significantly lower than it was even six months ago. Hospital admissions and deaths have not increased significantly either, but then in Portugal it took three weeks after the BA.5 peak in cases for deaths to peak. A stronger ability to reinfect also means that BA.5 has a larger pool of potential carriers. While other variants are limited by the protection afforded by vaccination, BA.5 can return through populations that assume they are more protected than they actually are. “BA.4/5 caused a significant wave of cases in South Africa, regardless of their high level of immunity,” Kaitlyn Jetelina observed about two weeks ago. Jetelina tweets and blogs under the name Your Local Epidemiologist. He goes on to note that “in South Africa, wave BA.4/5 contributed excess deaths, but fewer than previous waves.” In Europe, Portugal is the country most affected by the new Omicron sub-variants. It peaked in cases on May 16, according to the World Health Organization. Deaths in that country peaked almost exactly three weeks later, on June 6. What does this mean for the US? Our future is more difficult to predict based on the experiences of other countries than in the past. Portugal was hit much harder than the United States in the winter of 2000-2001 and less hard than last winter’s Omicron wave, which devastated the US. 5. Previous infections with Omicron may provide more protection. Our Omicron winter wave was also more recent, which helps. But Portugal has a higher rate of aid than the US One thing’s for sure: This won’t be the last variant we see. Topol warns that “new versions of the virus … are accelerating and we are not done yet, by any means.” Indeed, like tropical storms in the Caribbean this summer, there are already a number of new variants on their way. And experts say significant mutations — especially in the Omicron subvariants — are coming at an increasing rate. A new strain known as BA.5.1 caused the largest-ever outbreak in Macau last week, prompting local officials to put a large part of the region under lockdown. BA.5.1 appeared in small numbers in the US, as well as the UK and Portugal. The strain has been described as “the daughter of BA.5” and Christine Pagel, Professor and Director of the Clinical Operations Research Unit at University College London, wrote in an article last month that “it appears that BA.5 and 5.1 will likely win to become the general dominant variants’. Since then, however, BA.2.75 has reared its head. Although not yet found in the US, the BA.2 sub-variant has been detected in England, Germany and India, where it has reportedly been found in 18% of samples. And it’s spreading fast. See the chart below for the graph of its growth in India. More, unfortunately, to come. Here is the latest photo for the new BA.2.75 subclass (alias: “Centaurus”) – an evolutionary leap from the BA.2. It has been detected most frequently in India, showing extremely rapid growth in 18% of recent samples. It is also spreading rapidly to other countries.🧵 pic.twitter.com/JnkLsU9Lnw — Mike Honey (@Mike_Honey_) July 2, 2022
