How does the BA.5 COVID-19 variant differ from other strains?

How does the BA.5 COVID-19 variant differ from other strains?

Omicron’s rapidly-expanding BA.5 subvariant and its close relative BA.4 now make up about 95% of COVID-19 cases in the United States, according to estimates released Tuesday by the Centers for Disease Control and Prevention.

The strains have driven an acceleration this month in the pace of new COVID-19 cases — President Biden between them. Hospitalizations in some regions have now overtaken the worst days of delta variant waves last year, particularly among Americans age 70 and older.

CDC officials say they are now studying the current wave, with preliminary results due later next month on how issues like vaccine effectiveness are affecting the variations. And data from other countries that have already survived a wave of cases from BA.5 and its close relative BA.4 may signal what’s to come.

However, the nature of the epidemic has changed in important ways, and there are now many people with prior infection, protection from vaccines, or both. This is a muddy attempt to study viruses.

Fever and sore throat go beyond loss of taste and smell

Data from the UK study, as well as the country’s ongoing COVID-19 survey, suggest that the share of sick residents there A once-hallmark symptom of loss of taste and smell has decreased significantly since before the pandemic.

It was first observed by scientists around the world during a wave of Omicron BA.1 subvariant infections in the winter. Instead, flu-like symptoms of COVID-19 are now more commonly reported.

“The percentage of people who tested positive who reported abdominal pain, fever, sore throat and muscle pain increased in June 2022 compared to May 2022,” the country’s National Statistics Office reported as of June 24.

But it’s hard to tell how much of that change is due to changes in the virus. Scientists hypothesize that immunity from previous infections may also play a role in influencing the common symptoms seen during the latest Omicron wave.

Reinfection is increasing

Reinfection rates in the UK and other countries have increased since the arrival of the Omicron variant in the winter.

Federal researchers estimate that the mutations in BA.4 and BA.5 are the furthest from the parent strain of the virus in 2020 and even closer to the beta form first seen in May 2020 than its Omicron cousin BA.1.

Data from Qatar suggest that people who survived a previous COVID-19 infection with the Omicron variant have about 15% protection against symptomatic re-infection by BA.4 or BA.5. If the previous infection was from another omicron subvariant, that estimate increased to 76%.

Health authorities here, for example in Washington state, have also noted a steady increase in reinfections over the past few months, although they acknowledge that this may be underestimated due to factors such as home testing.

“What’s the closest parallel to what we’re seeing in the US? The UK is the closest, but the UK itself is very far removed from what we’re seeing here in the US,” said Venky Soundarajan, chief scientific officer at the research firm. Neference

Soundarajan recently worked with National Institutes of Health scientists to publish research in PNAS Nexus that measures the “distinctiveness” of variants that have previously spread to a particular region of the world. The authors found that this new metric could predict future increases in variants in different parts of the world, depending on whether the variant had previously spread to that region.

Soundarajan cited the wide gap in new COVID-19 cases between the two countries in March, with the UK reporting a sharp increase in BA.2 infections at a time when cases in the US were largely slowing.

Their metric suggests that although BA.5’s significant growth advantage will increase in the field, the “wall of immunity” that formed during the winter wave suggests that the current wave will not reach the same record height.

“The BA.5 Omicron is not significantly different in the US from what we’ve seen, especially with BA.2.12.1 being the most recent subtype to circulate. And BA.1 continues to provide a very high exposure that we suspect will continue to play into the summer. ,” added Soundarajan.

Rates of severe disease remain lower than in previous waves

Even as the pace of COVID-19 hospitalizations across the country accelerates, measures of some of the disease’s worst outcomes remain far lower than in some earlier waves in the pandemic.

A relatively small percentage of hospital intensive care unit beds across the country are occupied by COVID-19 patients. The pace of new COVID-19 deaths remains worse than this time last year, with an “unacceptable” average of more than 300 deaths per day. But even among more vulnerable groups, such as nursing home residents, the daily death toll from COVID-19 remains a fraction of previous waves.

Federal health authorities have created this “decoupling” to protect against the widespread use of vaccinations, particularly additional booster doses, as well as COVID-19 treatments such as Pfizer’s Paxlovide pill.

A study published last week in the New England Journal of Medicine suggests that currently available COVID-19 drugs will work against the BA.4 and BA.5 subvariants.

Data from a wave of two subvariants in South Africa earlier this year suggested they posed a similar risk of COVID-19 hospitalizations and severe disease compared to Omicron’s original BA.1 subvariant.

However, preliminary studies from countries such as Denmark and Portugal now suggest that BA.5 may pose a greater risk of hospitalization than BA.2. And preliminary lab tests with subvariants, as scientists in Australia recently revealed, may pose an even greater threat to BA.5’s ability to infect lung tissue.

Home tests may be more useful in identifying BA.5

During the first wave of Omicron BA.1 subvariant infections Back in DecemberFederal health officials acknowledged that preliminary data suggested that rapid tests in some homes appeared to have less sensitivity in detecting infections than earlier forms.

“As we saw early in the Omicron era, it looked like antigen test sensitivity was going down. It’s been posted on the FDA website for months now. And the data continues to accumulate that it’s not as sensitive,” Tim Stenzel of the Food and Drug Administration said last month. A town hall spoke with the makers of the COVID-19 test.

However, in a recent webinar with COVID-19 testing laboratories, Stenzel said the regulator has seen preliminary — if not yet settled — data that could change with BA.5, meaning home tests are more likely to detect this subvariant. .

The regulator is working with the National Institutes of Health’s RADx program at Emory University and the Georgia Institute of Technology to study the effects of the variants in testing.

“There are some reports that there may be fewer positives. And some preliminary data indicates that it may be. So we’re seeing improved antigen test performance with BA.5,” Stenzel said last week.

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