A Combination Of Tests Key To Preventing Future Flare-Ups of COVID-19
Wednesday, April 22, 2020
Photo by John Locher AP
Many officials around the country have released timelines for when people can end their isolation. Health experts say robust testing is necessary to prevent another surge in cases, but that may not be a catch-all solution.
For most people, facing a pandemic is a new experience. But for Californians, there’s a familiarity with this crisis, because it’s similar to fire season, Sumit Chanda said.
“You see these brush fires, right? And SDG&E and fire departments are surveying the backcountry, and as soon as they see one of these flares up, they bring in the cavalry and they tamp that down.”
Chanda, a virus expert at the Sanford Burnham Prebys Medical Discovery Institute, said without herd immunity, it’s impossible to prevent these flare-ups from happening.
Herd immunity occurs when enough people have become infected to develop antibodies that can fend off the virus. Or there’s a vaccine that helps people become immune.
“Herd immunity is like clearing your backyard of brushes," he said. "So every person that has antibodies to the virus, either through the vaccine or being infected previously, those are people that can no longer burn.”
Social distancing has slowed down the rate of infections. But society has to open back up. And the problem? There’s still no herd immunity. Not enough people were exposed to the virus to develop immunity naturally. And, a vaccine won't be developed for months to more than a year.
Vigorous testing is necessary now, and especially when isolation ends, Chanda said.
“Essentially you’re superman for the next year when it comes to COVID-19, or you’re a potential brush fire and you need to be contained as quickly as possible," Chanda said. "That’s from a scientific point of view what those tests tell you,"
A combination of tests key to maintaining spread
Chanda was referring to two main tests. The first is a PCR — or polymerase chain reaction — test. David Pride, a pathologist at UC San Diego, said this test is used to detect a number of viruses.
"[Viruses] are basically like little organisms, and a little amount of these can do a lot of damage," Pride said. "And the way we can detect them is to, in essence, take RNA and make a whole lot more so that it's readily apparent that the [virus] is there."
PCR tests take genetic material, such as RNA, from cells collected on swabs. Scientists sort of magnify the samples by creating a lot of the genetic material to detect trace amounts of the virus. Faster point-of-care tests, with advanced instrumentation, can deliver results in less than an hour.
But PCR tests only diagnose whether someone has the virus now, not whether they did in the past. That’s where a blood test comes in. These can detect antibodies that show that a person got infected in the past and was able to fight the infection off.
“We're not really trying to detect the virus in your blood," Pride said. "What we're trying to detect is your body's response to the virus and your blood."
Pride said these tests are important to show which person might be less vulnerable, or less likely to spread the virus when they go back to work. It also means people who are immune may be able to donate their antibodies to people who aren’t.
Those are things that have been done in the past for other infections such as Ebola.
Pride said a combination of these tests is key to monitoring coronavirus. PCR tests will show who’s infected and needs to be quarantined, while blood tests show who's less susceptible.
Public participation still a major part of the puzzle
But there’s another factor that’s necessary for these measures to keep fires from starting, said Dr. Michael Busch, and senior researcher and director at Vitalant, a blood donation company.
That factor is public participation.
"Ok, we want to test the 300 million people in this country?" Busch said. "You've got to get all those people sampled. You've got to get them to go into a laboratory or a clinic setting where they have their blood drawn."
Blood bank networks are built to more easily get samples from people and process them, Busch said. COVID-19 testing doesn’t have that network.
Early evidence from South Korea shows some people can get infected twice. Busch said while mass testing can squash a lot of flare-ups. It won’t prevent all of them.
"It'll be a dance," he said. "There'll be ongoing both public health and individual testing going on, and that'll continue."
But Busch said it will take a while before the world returns to what was normal.
"It will not be as if all of a sudden we test everybody and the party's over," he said. "The dance will go on until we have an effective vaccine."
Until then, he said, there’ll have to be active public participation alongside testing. That means lots of handwashing, limited public gatherings, and the need for people to monitor their symptoms.
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