HomeHealthHow is the BA.5 COVID-19 variant different from other strains?

How is the BA.5 COVID-19 variant different from other strains?


Omicron’s fast-spreading BA.5 subvariant and its close relative BA.4 now account for about 95% of COVID-19 cases in the US, according to Dear released Tuesday by the Centers for Disease Control and Prevention (CDC).

Strains have fueled an acceleration this month in the pace of new COVID-19 cases: President Biden among them. hospital admissions in some regions they now dwarf the worst days of last year’s variant Delta wave, especially among Americans 70 and older.

CDC officials say they are now studying the current wave, with preliminary results on how the variants are affecting issues like vaccine efficacy due to be released late next month. And data from other countries that have already survived a wave of cases of BA.5 and his close relative BA.4 could offer clues as to what is to come.

However, the nature of the pandemic has changed in important ways and there are now a large number of people with previous infectionsvaccine protection, or both. East is clouding attempts to study the virus.

Fever and sore throat outweigh loss of taste and smell

Data from studies in the UK, as well as from the country ongoing COVID-19 surveysuggest that the proportion of ill residents who reported the Symptoms that were once characteristic of loss of taste and smell. has dropped significantly since the beginning of the pandemic.

East it was a change first observed by scientists around the world during the winter wave of Omicron BA.1 subvariant infections. Instead, the flu-like symptoms of COVID-19 are now being reported more frequently.

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

But it’s hard to say how much of that change is due to a change in the virus itself. Scientists have hypothesized that immunity from previous infections might as well be playing a role in affecting what appear to be the common symptoms seen during the last waves of Omicron.

Increase in reinfections

The rate of reinfections has emerged in the UK and other countries since the arrival of the Omicron variant during the winter.

Federal researchers have estimated that mutations of BA.4 and BA.5 place them among the farthest of the original strain of the virus in 2020, and closer even to the Beta variant first seen in May 2020 than its cousin Omicron BA.1.

Qatar Facts suggests people who survived a COVID-19 infection prior to the Omicron variant have only about 15% protection against symptomatic reinfection with BA.4 or BA.5. If the previous infection was from another Omicron subvariant, that estimate increases to 76%.

The health authorities here, for example, in washington statethey also noted a steady rise in reinfections in recent months, although they acknowledge this may be an underestimate 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 a long way from what we’re seeing here in the US,” said Venky Soundararajan, scientific director of the research company. Nference.

Soundararajan recently worked with scientists from the National Institutes of Health to publish research in PNAS Nexus quantify the “distinctiveness” of variants, relative to those that have previously spread within a specific region of the world. The authors found that this new metric could predict variations in future variant surges in different parts of the world, depending on which variants had previously spread in those regions.

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

His metric suggests that while BA.5’s significant growth advantage will drive a surge in cases, the “immunity wall” built during the winter wave suggests the current wave won’t reach the same record heights.

“BA.5 Omicron is not significantly different in the US from what we have seen, particularly with BA.2.12.1, which was the most recent subtype to circulate. And BA.1 continues to provide an extremely high level of exposure. higher than us. The suspect will continue through the summer,” Soundararajan added.

Severe illness rates remain lower than in previous waves

Even as the pace of COVID-19 hospitalizations has accelerated across the country, measurements of some of the worst outcomes of the disease remain much lower than during some previous waves of the pandemic.

Only a relatively small percentage of hospital intensive care unit beds Around the country they are occupied by patients with COVID-19. the rhythm of new deaths from covid-19 It’s still worse than this time last year, by a “unacceptable” average of more than 300 deaths per day. But even among the most vulnerable groups like nursing home residentsthe daily number of deaths from COVID-19 remains a fraction of some previous waves.

Federal health authorities have attributed this “decoupling” to the protection offered by vaccination, especially additional booster dosesas well as wider use of COVID-19 treatments such as Paxlovid pills from Pfizer.

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 the South African case wave of the two sub-variants at the beginning of this year suggest they posed a similar risk of COVID-19 hospitalization and severe illness compared to Omicron’s original BA.1 subvariant.

However, early research from countries such as Denmark Y Portugal now suggest that BA.5 may pose a higher risk of hospitalization compared to BA.2. And the first laboratory tests with the subvariant, such as those recently published by scientists in australiasuggest that BA.5 could pose a greater danger due to its ability to infect lung tissue.

Home tests may be more effective in detecting BA.5

During the wave of infections by the first subvariant Omicron BA.1 in DecemberFederal health officials acknowledged that early data suggested some rapid home tests appeared to have lower sensitivity for detecting infections compared to earlier variants.

“We had seen, early in the Omicron era, that it seemed like the antigen tests were seeing a decline in sensitivity. That has been posted on the FDA website for months. And the data has continued to accumulate that there is no It’s so sensitive.” Tim Stenzel of the Food and Drug Administration told a town hall last month with manufacturers of COVID-19 tests.

However, in a recent webinar with COVID-19 testing labs, Stenzel said the regulator had seen early, though not yet conclusive, data suggesting that might have changed with BA.5, meaning that home tests are more likely to detect this subvariant.

The regulator has been working with the National Institutes of Health RADx Program at Emory University and the Georgia Institute of Technology to study the impact of variants on testing.

“There are some reports that there may be fewer low positives. And some of the early data suggests that may be the case. So we could see better antigen test performance with BA.5,” Stenzel said last week. pass.



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