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Saturday, March 15, 2025

What’s known about ‘stealth’ version of omicron?

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1143 days ago
20220126
A medical worker wearing protective gear collects a sample from a resident at a coronavirus test site in Xichen District in Beijing, Tuesday, Jan. 25, 2022. Hong Kong has already suspended many overseas flights and requires arrivals be quarantined, similar to mainland China's "zero-tolerance" approach to the virus that has placed millions under lockdowns and mandates mask wearing, rigorous case tracing and mass testing. (AP Photo/Andy Wong)

A medical worker wearing protective gear collects a sample from a resident at a coronavirus test site in Xichen District in Beijing, Tuesday, Jan. 25, 2022. Hong Kong has already suspended many overseas flights and requires arrivals be quarantined, similar to mainland China's "zero-tolerance" approach to the virus that has placed millions under lockdowns and mandates mask wearing, rigorous case tracing and mass testing. (AP Photo/Andy Wong)

An AP EX­PLAIN­ER by LAU­RA UN­GAR

 

(AP) — Sci­en­tists and health of­fi­cials around the world are keep­ing their eyes on a de­scen­dant of the omi­cron vari­ant that has been found in at least 40 coun­tries, in­clud­ing the Unit­ed States.

This ver­sion of the coro­n­avirus, which sci­en­tists call BA.2, is wide­ly con­sid­ered stealth­i­er than the orig­i­nal ver­sion of omi­cron be­cause par­tic­u­lar ge­net­ic traits make it some­what hard­er to de­tect. Some sci­en­tists wor­ry it could al­so be more con­ta­gious.

But they say there’s a lot they still don’t know about it, in­clud­ing whether it evades vac­cines bet­ter or caus­es more se­vere dis­ease.

 

WHERE HAS IT SPREAD?

 

Since mid-No­vem­ber, more than three dozen coun­tries have up­loaded near­ly 15,000 ge­net­ic se­quences of BA.2 to GI­SAID, a glob­al plat­form for shar­ing coro­n­avirus da­ta. As of Tues­day morn­ing, 96 of those se­quenced cas­es came from the U.S.

“Thus far, we haven’t seen it start to gain ground” in the U.S., said Dr. Wes­ley Long, a pathol­o­gist at Hous­ton Methodist in Texas, which has iden­ti­fied three cas­es of BA.2.

The mu­tant ap­pears much more com­mon in Asia and Eu­rope. In Den­mark, it made up 45% of all COVID-19 cas­es in mid-Jan­u­ary, up from 20% two weeks ear­li­er, ac­cord­ing to Statens Serum In­sti­tut, which falls un­der the Dan­ish Min­istry of Health.

 

WHAT’S KNOWN ABOUT THIS VER­SION OF THE VIRUS?

 

BA.2 has lots of mu­ta­tions. About 20 of them in the spike pro­tein that studs the out­side of the virus are shared with the orig­i­nal omi­cron. But it al­so has ad­di­tion­al ge­net­ic changes not seen in the ini­tial ver­sion.

It’s un­clear how sig­nif­i­cant those mu­ta­tions are, es­pe­cial­ly in a pop­u­la­tion that has en­coun­tered the orig­i­nal omi­cron, said Dr. Je­re­my Luban, a vi­rol­o­gist at the Uni­ver­si­ty of Mass­a­chu­setts Med­ical School.

For now, the orig­i­nal ver­sion, known as BA.1, and BA.2 are con­sid­ered sub­sets of omi­cron. But glob­al health lead­ers could give it its own Greek let­ter name if it is deemed a glob­al­ly sig­nif­i­cant “vari­ant of con­cern.”

The quick spread of BA.2 in some places rais­es con­cerns it could take off.

“We have some in­di­ca­tions that it just may be as con­ta­gious or per­haps slight­ly more con­ta­gious than (orig­i­nal) omi­cron since it’s able to com­pete with it in some ar­eas,” Long said. “But we don’t nec­es­sar­i­ly know why that is.”

An ini­tial analy­sis by sci­en­tists in Den­mark shows no dif­fer­ences in hos­pi­tal­iza­tions for BA.2 com­pared with the orig­i­nal omi­cron. Sci­en­tists there are still look­ing in­to this ver­sion’s in­fec­tious­ness and how well cur­rent vac­cines work against it. It’s al­so un­clear how well treat­ments will work against it.

Doc­tors al­so don’t yet know for sure if some­one who’s al­ready had COVID-19 caused by omi­cron can be sick­ened again by BA.2. But they’re hope­ful, es­pe­cial­ly that a pri­or omi­cron in­fec­tion might lessen the sever­i­ty of dis­ease if some­one lat­er con­tracts BA.2.

The two ver­sions of omi­cron have enough in com­mon that it’s pos­si­ble that in­fec­tion with the orig­i­nal mu­tant “will give you cross-pro­tec­tion against BA.2,” said Dr. Daniel Ku­ritzkes, an in­fec­tious dis­eases ex­pert at Brigham and Women’s Hos­pi­tal.

Sci­en­tists will be con­duct­ing tests to see if an­ti­bod­ies from an in­fec­tion with the orig­i­nal omi­cron “are able to neu­tral­ize BA.2 in the lab­o­ra­to­ry and then ex­trap­o­late from there,” he said.

 

HOW CON­CERNED ARE HEALTH AGEN­CIES?

 

The World Health Or­ga­ni­za­tion clas­si­fies omi­cron over­all as a vari­ant of con­cern, its most se­ri­ous des­ig­na­tion of a coro­n­avirus mu­tant, but it doesn’t sin­gle out BA.2 with a des­ig­na­tion of its own. Giv­en its rise in some coun­tries, how­ev­er, the agency says in­ves­ti­ga­tions of BA.2 “should be pri­or­i­tized.”

The UK Health Se­cu­ri­ty Agency, mean­while, has des­ig­nat­ed BA.2 a “vari­ant un­der in­ves­ti­ga­tion,” cit­ing the ris­ing num­bers found in the U.K. and in­ter­na­tion­al­ly. Still, the orig­i­nal ver­sion of omi­cron re­mains dom­i­nant in the U.K.

 

WHY IS IT HARD­ER TO DE­TECT?

 

The orig­i­nal ver­sion of omi­cron had spe­cif­ic ge­net­ic fea­tures that al­lowed health of­fi­cials to rapid­ly dif­fer­en­ti­ate it from delta us­ing a cer­tain PCR test be­cause of what’s known as “S gene tar­get fail­ure.”

BA.2 doesn’t have this same ge­net­ic quirk. So on the test, Long said, BA.2 looks like delta.

“It’s not that the test doesn’t de­tect it; it’s just that it doesn’t look like omi­cron,” he said. “Don’t get the im­pres­sion that ‘stealth omi­cron’ means we can’t de­tect it. All of our PCR tests can still de­tect it.”

 

WHAT SHOULD YOU DO TO PRO­TECT YOUR­SELF?

 

Doc­tors ad­vise the same pre­cau­tions they have all along: Get vac­ci­nat­ed and fol­low pub­lic health guid­ance about wear­ing masks, avoid­ing crowds and stay­ing home when you’re sick.

“The vac­cines are still pro­vid­ing good de­fense against se­vere dis­ease, hos­pi­tal­iza­tion and death,” Long said. “Even if you’ve had COVID 19 be­fore — you’ve had a nat­ur­al in­fec­tion — the pro­tec­tion from the vac­cine is still stronger, longer last­ing and ac­tu­al­ly ... does well for peo­ple who’ve been pre­vi­ous­ly in­fect­ed.”

The lat­est ver­sion is an­oth­er re­minder that the pan­dem­ic hasn’t end­ed.

“We all wish that it was over,” Long said, ”but un­til we get the world vac­ci­nat­ed, we’re go­ing to be at risk of hav­ing new vari­ants emerge.”

___

The As­so­ci­at­ed Press Health and Sci­ence De­part­ment re­ceives sup­port from the Howard Hugh­es Med­ical In­sti­tute’s De­part­ment of Sci­ence Ed­u­ca­tion. The AP is sole­ly re­spon­si­ble for all con­tent.

COVID-19Health


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