For weeks, health authorities have held April 15 in ominous regard as the date the U.K. strain would be dominant here. It’s April 9. The time has come.

Across the city, labs are reporting a majority of positive COVID tests are B.1.1.7 or the U.K. strain, which is 50% more contagious than the Wuhan or wild strain and thought to be more lethal.

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“All of the sequence runs that are coming out of UT Health Science Center, coming out of public health care, coming from the other sequencing labs, they’re all showing the same trend,” said David Sweat, deputy director of the Shelby County Health Department.

All but one sample tested at Poplar Healthcare Wednesday, April 7, were variants, predominantly the U.K. strain.

“We have been trending upward over the past several sequencing runs. This was the highest percentage for the U.K. variant,” said Jim Sweeney, head of the lab.

The three vaccines in use are effective against B.1.1.7, but less effective against the Brazilian strain, P.1, which is also in the local community. 

“It’s actually been introduced independently at least three to five times. And the good news there so far is that cases have been isolated and contacts have been quarantined,” Sweat said. “When we’ve done some circle testing around those individuals who have sequenced with that virus, we have not found any additional positives.

“That proves that the mix of tools we have to control the spread of the virus is being effective,” he said.

In Shelby County, labs had been sending suspicious samples, plus 100 random samples for genome sequencing.

Now, all positive COVID specimens are being sequenced, which gives health experts a better idea of how prevalent the variants are.

The issue now is that community testing is down, which means many variant cases could be flying below the radar.

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“I am somewhat encouraged that the British variant is outcompeting all those other strains,” said Dr. Scott Strome, executive dean of the College of Medicine at UTHSC. “In some ways, that is what we want because the vaccine works against it.”

The reproductive rate in Shelby County, even with the more transmissible virus, has dropped from 1.07 to 1.03. Anything over 1 means each positive person is still spreading the disease to at least one other.

Because the majority of people 75 and older have been vaccinated in Shelby County, most new cases are in younger people. Since they typically do not get as sick with COVID as older people, experts do not expect the hospitalization rate will rise as much or as fast if there is a fourth wave of disease.

The test will be in two to three weeks, says Dr. Manoj Jain, infectious disease expert on the front lines in hospitals here.

What’s puzzling now is why the COVID hospitalization rate for the last four or five weeks has stayed flat at 140-150 patients, said Dr. Fridtjof Thomas, epidemiologist and professor in the Department of Preventive Medicine at UTHSC.

Based on numbers testing positive, “we would expect to see 100 people in the hospital. But the numbers are not going down. People are not leaving the hospital. It’s not an inflow problem, it’s an outflow problem.”

The reality of the variants, even if they do not evade the vaccine, is they keep COVID alive, Jain says.

“We would be celebrating right now if the mutant strains had not arrived,” he said. “Just think, we would be talking about how we are out of this with the vaccine and the number of cases going down.”

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The nation is not celebrating. The Centers for Disease Control and Prevention reports 16,275 cases of B.1.1.7 as of April 6, creating particular worries for Michigan, California, Colorado, Minnesota, Massachusetts and Florida.

“We can envision the numbers going down if we can get the mutant strains under control,” Jain says, but the “cat is out of the bag” for B.1.1.7.

“But for the others, if we can do very aggressive contact tracing with isolation and quarantine as soon as we find a case, and all contacts are tested and wait 14 days, there is no opportunity to spread the infection.

“It literally comes to an end. That is what we need to be doing.”

It isn’t universally happening. In one case, Jain says two people in a Shelby County workplace were infected, and the employer did not encourage those around them be tested.

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“That is a very bad idea. With two people ill with COVID in the same workplace, they should all be tested,” he said.

Every new cluster of COVID, Jain says, should kick off a search-and-destroy mission.

“It’s very targeted approach. We can do this because the numbers are low enough,” he said.

“First, we need to do this for all the P.1 cases, then the other mutant strains and then as much as we can for the B.1.1.7 and the wild strain.”