The Centers for Disease Control and Prevention recently changed its coronavirus testing guidelines this week to exclude people who do not have symptoms of COVID-19 – even if they have recently been exposed to the virus.
Experts questioned the review, pointing out the importance of identifying infections in a small window immediately before symptoms break out, when many people are contagious.
The models suggest that about half of the infections can be traced to individuals who are still at this symptomatic stage before they start to get sick – if they ever have the disease at all.
“This is potentially dangerous,” said Dr. Krutika Kuppalli, an infectious disease physician in Palo Alto, California. Restricting testing to people with obvious COVID-19 symptoms means “you’re looking for a lot of people who are potential vectors of the disease,” he added. “I feel like this is making things worse.”
At a time when experts have almost generally come to encourage more frequent and extensive testing, especially to reach vulnerable and marginalized populations, the CDC update appears to be counter-intuitive and “very strange,” said Susan Butler-Wu, clinical microbiologist at the University of Southern California Keck Medical School. school.
Just weeks ago, the National Institutes of Health announced the first grant to the Rapid Acceleration of Diagnostics or RADx to expand coronavirus testing in the coming weeks and months. On the agency’s RADx website, officials stress the importance of prioritizing tests that can “detect asymptomatic people”.
Experts say a looser approach to testing could delay crucial treatments and obscure or even accelerate the spread of the coronavirus in the community.
“I find it weird,” said Daniel Larremore, a mathematician and infectious disease modeler at the University of Colorado Boulder. “Every move to reduce the level of testing by changing instructions is a step in the wrong direction.”
Previous iterations of the CDC testing guidelines clearly showed a different shade and clearly stated that “testing is recommended for all close contacts” regardless of the symptoms of people infected with the coronavirus. The Agency also emphasized in particular “possible asymptomatic and pre-symptomatic spread” as an important factor in the spread of the virus.
The latest version, released on Monday, changed the agency’s guidance by saying that people who have been in close contact with an infected person – typically defined as less than 6 meters from a person with a coronavirus and for at least 15 minutes – “may not need a test” if they have no symptoms.The agency noted that exceptions can be made for “vulnerable” individuals or if testing is recommended by health care providers or state or local public health authorities.
“Wow, it’s a walk,” Butler-Wu said. “We’re in the middle of a pandemic, and that’s a really big change.”
Butler-Wu said he was concerned that the instructions would be misinterpreted so that people with no symptoms could pass the coronavirus to others – a lie that experts had been trying to dispel for months. “If people are exposed and not tested, and they’re not isolated, it’s a huge problem,” Kuppalli said.
According to the CDC’s own estimates, about 40% of people infected with the coronavirus can never develop symptoms while remaining asymptomatic during treatment for the virus. These figures are preliminary – and it’s not ironic that they can’t be confirmed without testing more people who seem completely healthy.
Although researchers are uncertain about how often asymptomatic people inadvertently spread the coronavirus, studies have shown that silently infected people infect the virus in large quantities. The evidence is clearer for pre-asymptomatic people, whose virus levels peak just before the onset of the disease – a period when these individuals may mix with their peers and seed superhaw events. In particular, experts cannot distinguish asymptomatic people from people who are asymptomatic until symptoms appear or do not appear.
“Looking back, it just seems to ignore pre-symptomatic patients,” Butler-Wu said.
David Piegaro, who lives in Trenton, New Jersey, had been looking for several tests for the coronavirus in recent months, such as after a funeral and events that required travel because of his National Guard mission. She has never had symptoms and all of her tests have been negative, which has brought her peace of mind, especially when she lives with her parents and grandfather. “I considered testing a good task,” he said. “Asymptomatic people may spread the virus, so extensive testing seems valuable.”
Monitoring for asymptomatic cases is also important from the perspective of those infected, Kuppalli said. In less than a year of this pandemic, experts still do not know the full extent of the long-term effects of the spread of the coronavirus, even if the initial treatment appears benign.
The reasons for the unexpected change in testing recommendations are unclear. A CDC spokesman responded to a New York Times questionnaire asking questions about U.S. health and human services. An HHS spokesman said asymptomatic testing may still be warranted “when directed by public health managers or health care providers” and pointed out that testing decisions should be “based on individual circumstances and community status”.
On Twitter, some people speculate that the Trump administration made a change to try to correct a persistent supply shortage that has hampered testing efforts in many countries and extended lead times for weeks or more. Many testing institutions and companies have prioritized people with symptoms in their lineup as a way to speed up the return of results to those who are more susceptible to the seriously ill.
When asked about this, an HHS spokesman said the change was not a response to sputtering supply chains. “Testing capacity has expanded significantly and we are not taking advantage of all the capacity we have developed,” the spokesman said. “We revised the guidelines to match current evidence and best public health measures.”
Poorly timed tests, if performed infrequently, can lead to false positives or false negatives, lead to falsification of healthy people by infected people, or vice versa. This is a potential risk if someone is tested too soon after being exposed to a coronavirus, Butler-Wu pointed out.
Still, anyone with known exposure should be quarantined and consider applying for a test, Kuppalli said, adding: “We still need to be careful.”
Katherine J.Wu n 2020 The New York Times Company