Scientists in at least half a dozen universities and research centers in the United States have tested positive for the coronavirus — not because they were infected, but because they were studying the virus’s genetic material, and that contaminated their tests.
In recent months, labs around the country have begun research projects that involve the coronavirus’s genes, harmless hunks of molecules that pose no infectious threat. But those genes also happen to be the targets of several widely used coronavirus tests. Researchers who inadvertently inhale or touch the genetic material may be contaminating the swabs used to sample their airways, tricking tests into labeling them as infected, even when they are actually virus-free.
Contaminated positives such as these are extremely rare, health experts said. People outside the research community should not worry about their own test results. Blame also should not be pinned on the test, which did its intended job of rooting out the virus’s genetic material.
“This isn’t the fault of any test,” said Dr. Rosemary She, a pathologist and diagnostics expert at the University of Southern California who was not involved in the contamination events. “This is human error.”
But in a nation with a patchwork approach to testing, and where a great many researchers have rapidly pivoted to studying the coronavirus, contaminations are occurring with unexpected frequency. These issues have struck labs at Harvard University, M.I.T., Brown University, Roger Williams University, Cornell University and elsewhere, delivering puzzling results to anxious scientists, prompting building closures and fueling frustration with tests — which could cause people to avoid taking them altogether, damaging efforts to keep the virus in check.
“We’ve never had a situation where so many labs work on a pathogen” amid a pandemic and had so much asymptomatic testing, said Susan Butler-Wu, a clinical microbiologist at the University of Southern California who was not involved in the contamination events. As a result, there are few contingency plans in place to deal with such unusual testing errors.
Guidelines published by the Centers for Disease Control and Prevention recommend against retesting people within 90 days of a positive result. There are no explicit exceptions for potential contamination. Many individuals whose tests were probably contaminated, across several institutions, stopped getting tested for weeks or months, despite the possibility that they were still vulnerable to the virus, because their positive results had been treated as legitimate.
Without more flexibility in their policies to account for these unusual testing errors, Dr. Butler-Wu said, states and universities could soon “have an outbreak on their hands.”
