The Centers for Disease Control and Prevention this week quietly amended the coronavirus testing guidelines to exclude people who have no symptoms of Covid-19 – even if they have recently been exposed to the virus.
© Adriana Zehbrauskas for The New York Times
“When people are exposed, and they are not tested, and they are not isolated, that is a huge problem,” said one doctor.
Experts asked the review in question, pointing to the importance of identifying infections in the small window immediately before the onset of symptoms, as many individuals appear to be most contagious.
Models suggest that about half of transmission events can be traced back to individuals even at this so-called pre-symptomatic stage, before they start to feel sick – if they ever feel sick.
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“This is potentially dangerous,” he said. Krutika Kuppalli, a doctor for infectious diseases in Palo Alto, California. Limiting testing to only people with clear symptoms of Covid-19 means “you are not looking for many people who are potential spreaders of the disease,” she added. “I feel this will make things worse.”
At a time when experts have almost generally come forward to encourage more frequent and widespread testing, especially to reach vulnerable and marginalized sectors of the population, the CDC update seems counter-intuitive and “very strange,” said Susan Butler-Wu. , a clinical microbiologist at the Keck School of Medicine of the University of Southern California.
Just weeks ago, the National Institutes of Health announced the first round of grant recipients for its Rapid Acceleration of Diagnostics program, or RADx, to test coronavirus in the coming weeks and months. On the agency’s RADx website, officials stressed the importance of giving priority to tests that “can detect people who are asymptomatic.”
A slower approach to testing, experts say, can delay crucial treatments, as well as the obstruction, or even the speed of the spread of coronavirus in the community.
“I find it bizarre,” said Daniel Larremore, a mathematician and model of infectious diseases at the University of Colorado Boulder. “Any move now to reduce levels of testing by changing guidelines is a step in the wrong direction.”
Previous iterations of the CDC’s test guidelines set a distinctly different tone, explicitly stating that “testing is recommended for all close contacts” of people infected with the coronavirus, regardless of symptoms. The agency also specifically highlighted “the potential for asymptomatic and pre-symptomatic transmission” as an important factor in the spread of the virus.
The latest version, released on Monday, changed the agency’s guidance to say that people who have been in close contact with an infected individual – typically defined as within six feet of a person with the coronavirus and on its at least 15 minutes – “do not necessarily need a test” if they have no symptoms. Exceptions, the bureau noted, can be made for “vulnerable” individuals, such as if health care providers or state public health officials recommend testing.
“Wow, that’s a return trip,” said Dr. Butler-Wu. “We are in the middle of a pandemic, and that is a very big change.”
Dr. Butler-Wu said she was concerned that the guidelines would be misinterpreted as implying that asymptomatic people could not pass on the coronavirus to others – a forgery that experts have been trying to dispel for months. “If people are exposed, and they are not tested, and they do not isolate themselves, that is a huge problem,” said Dr. Kuppalli.
According to the CDC’s own estimates, roughly 40 percent of people infected with the coronavirus can never develop symptoms, remaining asymptomatic for the duration of their tenure with the virus. These numbers are tentative – and ironically can not be confirmed without further testing from people who appear completely healthy.
Although researchers remain unsure how often asymptomatic people transmit the coronavirus, studies have shown that the silent infection can carry the virus in high doses. The evidence is clearer for pre-symptomatic people, in whom virus levels tend to peak just before disease begins – a period in which these individuals may mingle with their peers, and sow superspreader events. Notably, experts cannot distinguish asymptomatic people from those who are pre-symptomatic until symptoms appear or not.
“It seems backwards to just ignore pre-symptomatic patients,” said Drs. Butler-Wu.
David Piegaro, who lives in Trenton, NJ, had been looking for several tests for the coronavirus in recent months, after events such as funerals and those in need of travel because of his position in the National Guard. He has never experienced any symptoms, and his tests have all been negative, bringing him peace of mind, especially since he lives with his parents and grandparents. “I saw testing as a good thing to do,” he said. “Asymptomatic people can spread the virus, so widespread testing seems valuable.”
Following asymptomatic cases is also important from the perspective of the infected, Drs. Kuppalli. Less than a year into this pandemic, experts still do not know the full extent of the long-term consequences of contracting the coronavirus, even if the first encounter seems benign.
The reasons behind the surprising shift in test recommendations are unclear. In response to a question from The New York Times, a representative of the CDC addressed the questions to the US Department of Health and Human Services. A HHS spokesman said asymptomatic testing could still be guaranteed “as directed by public health leaders as healthcare providers,” and stated that testing decisions should be “based on individual circumstances and the status of community outbreaks.”
On Twitter, some people speculated that the Trump administration made the change to try to address persistent supply shortages, which have fueled testing efforts in many parts of the country, and extend stretch times for results to weeks or more. Many institutions and companies that perform tests have prioritized people with symptoms in their lineup as a way to speed up the return of results for those who are most at risk of falling seriously ill.
Asked about it, the HHS spokesman said the change was not a response to sputtering supply chains. “Test capacity has been massively expanded, and we are not using the full capacity we have developed,” the spokesman said. “We have revised the guidance to reflect current evidence and the best public health interventions.”
Poorly tested tests, if rarely performed, can lead to false positives as well as false negatives, causing healthy people to fail as infected or vice versa. This is a potential risk if someone is tested too soon after being exposed to the coronavirus, Drs. Butler-Wu to.
Even if anyone with a known exposure should quarantine and consider seeking a test, Drs. Kuppalli, adding: “We still have to be careful.”
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