BA.2 ‘stealth omicron’ variant is now more than half of COVID cases in North Texas
Only two months after it was first detected, “stealth” omicron now makes up over half of COVID-19 cases in North Texas, say researchers at UT Southwestern Medical Center.
The more transmissible omicron subvariant, known as BA.2, has been detected in 55% of positive test results in the Dallas-Fort Worth region, the lab told the Star-Telegram.
“We’re seeing it increase as the proportion of those cases we’re getting,” says Russ Jones, chief epidemiologist at Tarrant County Public Health. “In early March, late February, we started seeing increases. Now we believe it is the vast majority of cases.”
UT Southwestern Medical Center reports data to the Texas Department of State Health Services, which estimates that BA.2 makes up 84% of the state’s cases. That’s a few percentage points lower than the national rate of 86%. The Centers for Disease Control and Prevention reports that BA.2 makes up 83% of COVID cases in the Arkansas, Louisiana, New Mexico, Oklahoma and Texas region, compared to 71% just a week ago.
Jones expects that BA.2 will make up the totality of new county cases in the coming weeks, and 98% to 100% of cases by the end of April. That’s because stealth omicron is more transmissible than omicron and other variants, Jones says.
Overall, however, COVID cases in Tarrant County have plateaued over the last three weeks, Jones said. In the most recent data, for the week ending April 2, the county had reported 15 confirmed cases per 100,000 people, down from 17 cases the prior week, which was already a record low for the last two years. Had it not been for the subvariant, COVID cases would have declined further, at an estimated 10 cases per 100,000 people, Jones says.
Other indicators measured by the county also point to a plateau in cases. The COVID-19 community level is low. Fewer than 1% of emergency room visits are COVID-related, compared with 18% during the last wave in January. Fewer than 3% of COVID tests reported have come back positive. And the reproductive number is 0.95, meaning virus spread is decreasing. Once it reaches 1, that means virus spread is stable.
“We’re way down, our hospitals are way down,” Jones said. “It’s all been kind of plateaued.”
Jones likens stealth omicron to the alpha variant, which had been detected around March 2021 after a surge from January to February. After the variant appeared, there was a plateau in cases and then a decline.
Will Texas see a new COVID surge like other states?
In the Northeast, BA.2’s appearance amid the lifting of mask and social distancing mandates has been to blame for a recent surge. Because those mandates were never implemented in Texas, meaning less has changed for us, we likely won’t see a similar surge here, Jones says.
“A lot of those restrictions, people weren’t necessarily following to the same extent, as they probably did the Northeast. And therefore, we had a lot more infections occur of people who are vulnerable back in January,” Jones said. “So we’re watching to see what this means for us, we may get a bit of an increase but we don’t anticipate it being a large surge like we went through in the winter.”
When the health department gets notified of BA.2 cases in the county by the state, it investigates the circumstances of each case, such as whether it was in a congregate setting like a nursing home, homeless shelter or correctional facility. The department then gives guidance about what the patient can do to prevent others from being infected.
While people became symptomatic with past variants about five days after exposure, they can have symptoms within two days of exposure to omicron and its subvariant. And when they get sick faster, they shed more virus, Jones said, resulting in a rapid rise in cases.
Because of waning immunity, people who were infected with delta or other variants prior to omicron may get reeinfected with BA.2, Jones said, but illness likely won’t be as severe the second time around. There’s still a risk that people who weren’t infected could get infected with this variant due to its high transmissibility.
Texans who’ve been recently vaccinated or boosted are less likely to be infected with BA.2 because their immunity is still high, he said. When vaccine protection wanes, people could get infected with BA.2, but the risk of hospitalization is low.
People who were never infected and have not been vaccinated are at much higher risk of severe illness and hospitalization with BA.2.
‘How large it’ll be, we don’t know for sure’
We’re not seeing huge spikes week-by-week like we did with omicron in December, but there may be a gradual increase in stealth omicron cases, Jones said.
“How large it’ll be, we don’t know for sure, we’re watching it,” Jones said. “And at this point, we have not seen exponential growth.”
While stealth omicron is the only variant of concern currently, the county health department is on the lookout for new variants that could become predominant.
“If we get another variant like omicron that came out of left field that had quite a few mutations that gave it an advantage, then it could dodge our immune system of what we’ve been trained either by infection or trained by vaccine to recognize, and that would give it a competitive advantage and then we could get another wave.”
