Doctor says improper testing practices, changes in COVID variant leading to spread of BA.5

ByDustin Dorsey KGO logo

Saturday, August 6, 2022

Doctor says improper testing leading to spread of BA.5

A UCSF infectious diseases doctor says the new BA.5 variant is creating more false negative home tests, and it could be leading to more transmission.

SAN JOSE, Calif. (KGO) -- Why is the BA.5 COVID-19 variant spreading so quickly? A UCSF infectious disease expert is now saying it is testing -- not bad behavior -- that may be causing the rapid spread of the disease.

As the country continues to battle with the latest dominant COVID-19 variant BA.5, President Joe Biden said vaccinations, treatments and tests are key.

But what happens when one of those strategies doesn't work as intended?

San Jose's Isaac Velasquez says he and his fiancée never got a positive result on their home test, despite being exposed and showing symptoms of COVID.

"I ended up coming up negative twice. She was testing negative four times," Velasquez said. "It wasn't quite adding up, so we decided to go to the hospital to do some of the PCR tests. We ended up testing positive a couple days later."

This story is becoming common according to UCSF Infectious Diseases Specialist Dr. Peter Chin-Hong, and it's causing concern.

"I'm worried that a lot of transmission is occurring," Chin-Hong said. "Not because people are being devious or irresponsible, it's just that they don't know they're positive."

Chin-Hong said it's not that the tests aren't working, it's that the BA.5 variant is just behaving differently than other strains of the virus.

He says symptoms of BA.5 first show up in the throat, meaning a nose test won't show a positive result for several days.

"You can be swabbing your nose until there's no tomorrow, but if all the action is in your throat, it takes a while for that virus to go up to the nose," Chin-Hong said. "So that's why you're turning negative for a long time until you turn positive when the virus gets up to the nose."

Chin-Hong said the other factor is how a vaccinated person's immune system responds to this strain.

You might have symptoms, but there's not enough virus particles in your body for tests to show positive results.

"The rapid tests need 100,000 or more virus to turn positive, whereas a PCR just needs like five or less than 10 viruses to turn positive," Chin-Hong said.

For this reason, he suggests a PCR test may be better than a rapid test, or use the swab from the home test to swab swipe your throat then your nose to get a better result.

Chin-Hong also said testing at least five days after the start of symptoms could help prevent this highly transmissible variant from spreading even more.

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