Staggering spread of BA.5 subvariant shows why this California COVID wave is different

Rong-Gong Lin II and Luke Money

LOS ANGELES — With California suffering from another intense wave of coronavirus, the staggering proliferation of the BA.5 subvariant is becoming a growing focus of scientific scrutiny, with experts saying it can replicate itself far more effectively than versions previous omicron.

Compared to its ancestors, the latest omicron subvariant, BA.5, may have an enhanced ability to create large numbers of copies of the coronavirus once it enters human cells, a possible contributing factor as to why the wave of omicron this summer has been problematic.

BA.5, which in the estimation of federal health officials is currently the dominant version of the coronavirus across the country, arguably combines aspects of last summer’s delta variant with older versions of the highly contagious omicron family, he said. Dr. Eric Topol, director of the Scripps Translational Research Institute in La Jolla.

“You may remember the term ‘deltacron’ used prematurely many months ago in the pandemic. But the ability to infect cells for BA.5 is more akin to delta than to the earlier omicron family of variants,” Topol wrote in a blog post.

In many ways, this wave of the pandemic has felt different than other waves of omicron earlier this year. Health experts say the behavior of the ultra-contagious strain shows the need for prudent precautions.

Citing a preliminary report from Australia, Topol referred to data from a laboratory study that suggested BA.5 was found to produce far more copies of the coronavirus compared to an earlier omicron subvariant, BA.2.

“There are more copies of the virus because BA.5 has a much better ability to enter cells…which may help explain why this version of the virus has caused so much trouble, more so than other omicron subvariants,” Topol wrote in his publication. .

If BA.5 holds its position as the top dominant variant for a while, that could eventually stabilize the situation in California and eventually point to a situation where there will ultimately be a decline in cases, said Dr. Peter Chin-Hong, an infectious doctor. -disease expert at UC San Francisco.

But a possible key in this scenario is the appearance of another omicron sub-variant, BA.2.75, which has caused concern in India.

“And I know, it’s super discouraging,” Chin-Hong said. Still, she said, there are ways to live life while taking steps to reduce risk.

Common steps public health officials recommend include keeping up with vaccinations and boosters, getting tested before attending gatherings or events, and wearing masks when in crowded indoor or public places.

Furthermore, BA.5 appears to be duplicating earlier omicron traits of “immune escape,” the ability of the virus to escape the human body’s immune response induced by previous vaccinations or infections.

From early March to early May, California reported about 2,300 weekly reinfections. From mid-May to mid-June, the state reported about 10,400 weekly reinfections, around the time BA.5 and another closely related subvariant, BA.4, began to circulate widely.

The first omicron subvariant, BA.1, which spread rapidly in the US after Thanksgiving, already had dozens of mutations that made it difficult for our immune systems to recognize it.

“So what’s happened now is, with BA.5, you have overlapping mutations on BA.1 that make it even more difficult for our immune system to recognize,” Topol said.

Also problematic were early data from the Australian study suggesting reduced efficacy of Evusheld, a monoclonal antibody, against BA.5.

“So that’s another feature of immune escape, is that our monoclonal antibodies don’t work as well,” Topol said.

The question of whether BA.5 leads to more severe disease in humans has not been resolved.

The data from South Africa suggests that BA.5 has not changed the risk of hospitalization compared to earlier versions of omicron, Chin-Hong said.

Coronavirus case rates have remained at persistently high levels across the state for months, infecting significant numbers of people and hampering business operations. More and more positive coronavirus patients are seen in hospital.

During the week-long period ending Thursday, California reported an average of more than 15,500 new coronavirus cases per day. On a per capita basis, that’s about 278 cases per week per 100,000 population. That’s about 12% down from the previous week, but officials and experts say the apparent drop could be in part the result of data outages over the Fourth of July holiday weekend.

Los Angeles County’s rate of coronavirus cases has been relatively stable over the past week, but remains high at around 5,400 cases per day. On a per capita basis, that’s 373 coronavirus cases per week per 100,000 residents.

The official counts are almost certainly a far undercount due to the widespread use of home tests, the results of which are not reliably reported.

Statewide, 4,024 positive coronavirus patients were hospitalized as of Friday, the highest single-day total since late February. In Los Angeles County, the latest patient census was 1,014, an increase of 33% from two weeks earlier.

Although a significant portion of those patients are not hospitalized due to COVID-19 complications, and may have incidentally tested positive after seeking care for some other reason, officials say they nonetheless present a particular strain on resources due to additional services necessary to keep them from spreading the virus.

And as long as transmission remains elevated, health care systems are unlikely to see any major relief.

“With more cases, we’re obviously seeing more people who need medical attention, and not only in our hospitals, but also in our emergency departments and urgent care centers that are filled with many people who need care for their COVID-related illness.” , LA County Public Health Director Barbara Ferrer said during a recent briefing.

COVID-19 deaths, while still relatively low, are also starting to rise in Los Angeles County, from about 50 deaths a week in early June to nearly 100 deaths a week now. At the peak of the winter omicron wave, Los Angeles County reported more than 500 deaths per week.

In previous waves, dominant strains like delta last summer or alpha stuck around for relatively long periods and were not quickly displaced by their successors, meaning someone infected could enjoy a high degree of protection for perhaps several months.

That timeline has been shortened considerably in the omicron area. Since April alone, three different sub-variants, BA.2, BA.2.12.1, and now BA.5, have been estimated to be the dominant strain across the country. This rapid succession means that it is possible for someone to be infected with an earlier version of omicron and then re-infected with a later version several weeks later.

“Many people who were recently infected can probably get the virus again in three to four weeks, compared to the old days where they had a three-month window period” when reinfection is less likely, Chin-Hong said.

Chin-Hong said he knows people who, after their infection, thought he gave them a pass to “get out even more and not worry as much,” only to be left with a repeat infection. “That line of thinking isn’t very good when you have the changing of the guard” of the omicron sub-variants, she added.

While some people remain asymptomatic or have mild symptoms, others report severe discomfort, including a high fever, severe sore throat, and mental confusion and fatigue that can last for weeks, or possibly be the start of a long COVID, in which symptoms of the disease can persist for months or years.

It is also likely that some of those who have so far avoided infection are no longer employing certain protective measures they used before, or are exposed to family and friends who have relaxed protective practices.

People are “taking more risks; they are moving; they are traveling,” Chin-Hong said. Even in San Francisco, a number of people aren’t wearing masks in places where it was once ubiquitous, meaning there’s less peer pressure to wear a mask in areas where it was once commonplace, Chin-Hong said.