By now, everyone is familiar with the routine. Someone shows one or more symptoms of the coronavirus and gets tested. In due time, often several days, they receive a yes-or-no result. If they’re infected, it means two weeks of quarantine.
A reader sent an Aug. 29 article in The New York Times that questions the wisdom of this yes-or-no approach. It said tests that only determine an infection do not identify the important difference of who is carrying a relatively small amount of the virus, and who has a heavier infection that makes them more likely to spread the disease.
The story said most people “carrying relatively insignificant amounts of the virus” are not likely to be contagious. But testing them may contribute to delays that prevent those with higher viral loads from being identified quickly so that they can be isolated.
A Harvard epidemiologist says this does not mean there should be fewer tests, and he specifically criticized the Centers for Disease Control’s recent suggestion that people without symptoms do not need to be tested, calling that a backward idea.
Instead, the epidemiologist, Dr. Michael Mina, says the country badly needs to increase the use of tests that provide rapid results. Two days before the story published, the Trump administration apparently agreed, saying the government would buy 150 million rapid tests.
Hopefully that will alleviate the problem of people having to wait a week or more to get their test results. That kind of a delay hampers the effectiveness of testing.
When a patient is tested for the coronavirus, doctors typically tell them to stay home until the results come in. If a patient tests positive and faces a two-week quarantine, that means they could spend a total of three weeks in isolation.
That’s a long time for anybody who has bills to pay or kids to care for, and it’s understandable that some people will continue working until the results come in. The problem is that anybody who does this with a serious infection is putting others at risk.
The Times also dug into the mechanics of the testing procedure. A test that takes less analysis to find the virus means the patient has a higher viral load and is more infectious.
Most coronavirus tests currently identify a sample as positive if it requires a certain amount of analysis to identify the virus. Mina and Juliet Morrison, a virologist at the University of California Riverside, say the cutoff for a positive result should be 10 to 25 percent lower.
Reducing that cutoff would mean the viral load of a patient would have to be 100 to 1,000 times higher than the current standard used to report a positive result. The rapid test results would be helpful here: Someone tested too soon after becoming infected may not have a high load. But another test a day or two later would show whether the load has greatly increased, signifying an infectious disease risk.
A Columbia University virologist was surprised that no one is forwarding records on the amount of analysis required for each positive test. With that information, public health officials could warn patients with higher viral loads, and stress to them the importance of quarantine.
New York’s state lab reported 794 positive coronavirus tests in July. But if the samples required 12 percent less analysis to detect the virus, half of those tests would have been negative. At 25 percent less analysis, 70 percent of them would have been negative.
The implication is clear: Too many people who are not seriously infected are getting a positive test result. Medical experts also say it’s apparent that people who need the tests aren’t getting them. That must change before we can get a handle on this wearisome pandemic.