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CDC Expert Answers Top COVID-19 Questions

Alicia Gallegos
March 17, 2020

With new developments daily and lingering uncertainty about COVID-19, questions about testing and treatment for the coronavirus are at the forefront.

To address these top questions, Jay C. Butler, MD, deputy director for infectious diseases at the Centers for Disease Control and Prevention, sat down with JAMA editor Howard Bauchner, MD, to discuss the latest data on COVID-19 and to outline updated guidance from the agency. The following question-and-answer session was part of a live stream interview hosted by JAMA on March 16, 2020. The questions have been edited for length and clarity.

What test is being used to identify COVID-19?

In the United States, the most common and widely available test is the RT-polymerase chain reaction (rRT-PCR), which over the past few weeks has become available at public health labs across the country, Dr. Butler said during the JAMA interview. Capacity for the test is now possible in all 50 states and in Washington, D.C.

"More recently, there's been a number of commercial labs that have come online to be able to do the testing," Dr. Butler said. "Additionally, a number of academic centers are now able to run [Food and Drug Administration]–approved testing using slightly different PCR platforms."

How accurate is the test?

Dr. Butler called PCR the "gold standard," for testing COVID-19, and said it's safe to say the test's likelihood of identifying infection or past infection is extremely high. However, data on test sensitivity is limited.

"This may be frustrating to those of us who really like to know specifics of how to interpret the test results, but it's important to keep in mind, we're talking about a virus that we didn't know existed 3 months ago," he said.

At what point does a person with coronavirus test positive?

When exactly a test becomes positive is an unknown, Dr. Butler said. The assumption is that a patient who tests positive is more likely to be infectious, and data suggest the level of infectiousness is greatest after the onset of symptoms.

"There is at least some anecdotal reports that suggest that transmission could occur before onset of symptoms, but the data is still very limited," he said. "Of course that has big implications in terms of how well we can really slow the spread of the virus."

Who should get tested?

Dr. Butler said the focus should be individuals who are symptomatic with evidence of respiratory tract infection. People who are concerned about the virus and want a test are not the target.

"It's important when talking to patients to help them to understand, this is different than a test for HIV or hepatitis C, where much of the message is: 'Please get tested.'?" he said. "This a situation where we're trying to diagnose an acute infection. We do have a resource that may become limited again as some of the equipment required for running the test or collecting the specimen may come into short supply, so we want to focus on those people who are symptomatic and particularly on people who may be at higher risk of more severe illness."

If a previously infected patient tests negative, can they still shed virus?

The CDC is currently analyzing how a negative PCR test relates to viral load, according to Dr. Butler. He added there have been situations in which a patient has twice tested negative for the virus, but a third swab resulted in a weakly positive result.

"It's not clear if those are people who are actually infectious," he said. "The PCR is detecting viral RNA, it doesn't necessarily indicate there is viable virus present in the respiratory tract. So in general, I think it is safe to go back to work, but a positive test in a situation like that can be very difficult to interpret because we think it probably doesn't reflect infectivity, but we don't know for sure."

Do we have an adequate supply of tests in the United States?

The CDC has addressed supply concerns by broadening the number of PCR platforms that can be used to run COVID-19 analyses, Dr. Butler said. Expansion of these platforms has been one way the government is furthering testing options and enabling consumer labs and academic centers to contribute to testing.

When can people who test positive go back to work?

The CDC is still researching that question and reviewing the data, Dr. Butler said. The current recommendation is that a patient who tests positive is considered clear to return to work after two negative tests at least 24 hours apart, following the resolution of symptoms. The CDC has not yet made an official recommendation on an exact time frame, but the CDC is considering a 14-day minimum of quarantine.

"The one caveat I'll add is that someone who is a health care worker, even if they have resolved symptoms, it's still a good idea to wear a surgical mask [when they return to work], just as an extra precaution."

What do we know about immunity? Can patients get reinfected?

Long-term immunity after exposure and infection is virtually unknown, Dr. Butler said. Investigators know those with COVID-19 have an antibody response, but whether that is protective or not, is unclear. In regard to older coronaviruses, such as those that cause colds, patients generally develop an antibody response and may have a period of immunity, but that immunity eventually wanes and reinfection can occur.

What is the latest on therapies?

A number of trials are underway in China and in the United States to test possible therapies for COVID-19, Dr. Butler said. One of the candidate drugs is the broad spectrum antiviral drug remdesivir, which was developed for the treatment of the Ebola virus. Additionally, the National Institutes of Health is studying the potential for monoclonal antibodies to treat COVID-19.

"Of course these are drugs not yet FDA approved," he said. "We all want to have them in our toolbox as soon as possible, but we want to make sure these drugs are going to benefit and not harm, and that they really do have the utility that we hope for."

Is there specific guidance for healthcare workers about COVID-19?

Health care workers have a much higher likelihood of being exposed or exposing others who are at high risk of severe infection, Dr. Butler said. That's why, if a health care worker becomes infected and recovers, it's still important to take extra precautions when going back to work, such as wearing a mask.

"These are recommendations that are in-draft," he said. "I want to be clear, I'm floating concepts out there that people can consider ... I recognize as a former infection control medical director at a hospital that sometimes you have to adapt those guidelines based on your local conditions."

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Reviewed on 3/19/2020
References
SOURCE: Medscape, March 17, 2020.

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