There\u2019s a lot we still don\u2019t know about President Trump\u2019s Covid-19 case, starting with the basics: Is he having trouble breathing? Is he experiencing side effects, such as delirium or confusion, from the multiple experimental drugs for Covid-19 he\u2019s taking? When was his last negative coronavirus test?<\/p>\n
There\u2019s another burning question about Trump\u2019s health that matters more for the people around him, including his family members and staff at the White House who haven\u2019t yet tested positive: Is the president still contagious? <\/p>\n
Patients who have been diagnosed with Covid-19 are supposed to \u2014 per Centers of Disease Control and Prevention guidelines \u2014 isolate for at least 10 days since they first noticed they were sick or tested positive and until their symptoms have improved, including no fevers for at least 24 hours.<\/p>\n
In cases like Trump\u2019s that required hospitalization, that isolation period can last even longer. \u201cFor patients who had severe or critical illness, we wait up to 20 days to state they are noninfectious,\u201d said Sigal Yawetz, an attending physician at Brigham and Women\u2019s Hospital in Boston who has been caring for Covid-19 patients. <\/p>\n
Doctors rely on clinical symptoms because there\u2019s no clinically validated way to check if a patient is still contagious \u2014 even when the patient is the president. <\/p>\n
But we don\u2019t know exactly when Trump became symptomatic \u2014 one of the many basic facts about his case that\u2019s been muddled by confusing reports. If we go by what his doctors and colleagues have suggested, he started experiencing symptoms on Thursday, a day before entering hospital. <\/p>\n
That means Trump should probably still be isolating for at least two more days \u2014 perhaps longer. <\/p>\n
Instead, he rode in a car with others on day four of his symptoms, and on day five, took off his mask as he entered the White House. As of Wednesday, he\u2019d returned to the Oval Office to work \u2014 necessitating those around him to don N95 masks, gowns, and gloves. <\/p>\n
Safely donning and doffing personal protective equipment requires training and can be challenging for even highly experienced clinicians. Considering the White House\u2019s colossal failure at basic coronavirus prevention measures \u2014 such as social distancing, mask-wearing, and contact tracing \u2014 it\u2019s hard to imagine they\u2019ll successfully turn the residence and Oval Office into a model of infection control. <\/p>\n
But if the White House wants to prevent more coronavirus cases, they\u2019ll have to for this simple fact: Trump may still be contagious. <\/p>\n
There\u2019s no clinically validated way to test for Covid-19 contagion<\/p>\n
The best research we have so far on Covid-19 transmissibility suggests that people can shed infectious virus for up to nine days after getting sick. In general, they are most contagious two days before symptom onset, and in the first five days after, as the graph in the tweet below, from this Oxford University Press study, shows.<\/p>\n
But these are averages \u2014 and they hide a lot of the variability among patients. Some people are infectious for a shorter period, while others shed virus for up to 20 days after symptom onset.<\/p>\n
That\u2019s why doctors and public health officials ask patients to isolate for at least 10 days after their symptoms appear, or even longer in some cases. <\/p>\n
As for Trump, \u201cpotentially he passed through the most infectious stage already,\u201d said University of St. Andrew\u2019s virologist Muge Cevik. It\u2019s also possible the medications he\u2019s on, including the antiviral remdesivir, brought down his viral load quickly. \u201cBut he may be still contagious depending on his symptom onset.\u201d <\/p>\n
Doctors rely on the date symptoms appeared, or the first positive test in cases where people don\u2019t notice symptoms, because there\u2019s actually no proven way to show that a person is no longer infectious. The diagnostics available to check for infection \u2014 PCR tests \u2014 \u201ccan\u2019t distinguish between intact, infectious virus and degraded viral genetic material,\u201d Ilan Schwartz, an infectious disease doctor and professor at the University of Alberta, told Vox.<\/p>\n
Doctors could use something called the CT, or cycle threshold, that\u2019s part of the PCR test. It\u2019s a measure of a person\u2019s viral load, and if the number gets higher over time, the viral load in the sample is getting smaller. But the link between a person\u2019s CT number and their transmissibility is still not fully understood, said University of Michigan infectious disease doctor Kevin Gregg. <\/p>\n
\u201cThere are not completely established guidelines for [using CT values],\u201d he added. So it\u2019s not something doctors typically rely on to determine how long a patient should isolate.<\/p>\n
That\u2019s why \u2014 as a precaution \u2014 \u201c[Trump] should be isolating,\u201d Gregg said, \u201cso as not to infect members of his family, the staff of the White House, and other people.\u201d<\/p>\n
\u201cWe don\u2019t say, \u2018It\u2019s been 10 days, you can take off your mask\u2019\u201d<\/p>\n
There is one other, more advanced, way to check on a person\u2019s contagiousness: cell culturing. Scientists used the technique in many of the studies that informed the quarantine period. It involves infecting animal cells in Petri dishes with the SARS-CoV-2 virus, waiting for them to incubate, and seeing whether the virus can still grow in them. <\/p>\n
One of Trump\u2019s physicians, Jason Blaylock of Walter Reed National Military Medical Center, mentioned the president\u2019s medical team was working with \u201cvarious laboratories in the area, state of the art facilities … on obtaining advanced diagnostic testing to really inform the White House medical team of both the status of the president as well as his ability to transmit virus to others.\u201d <\/p>\n
He didn\u2019t specify, but perhaps cell culturing was what he was referring to. Yet even that isn\u2019t foolproof for use in patients. \u201cThere is a big difference between the virus being culturable in a Petri dish full of cells derived from a monkey\u2019s kidney and being capable of infecting the respiratory epithelium of living people,\u201d Schwartz said. \u201cThis test has absolutely not been validated for ruling out SARS-CoV-2 infectiousness in people.\u201d <\/p>\n
What\u2019s more, it takes several days to grow the virus and get a reliable result. \u201cSo I don\u2019t think they\u2019d have that information yet,\u201d said Gregg. <\/p>\n
Even after isolation, patients are still advised to wear a face mask. \u201cIf someone had Covid, after the contagious period is over, it doesn\u2019t mean you go out and do things as usual,\u201d said Preeti Malani, an editor at JAMA<\/em> and infectious disease doctor who treats Covid-19 patients. \u201cWe don\u2019t say, \u2018It\u2019s been 10 days, you can take off your mask.\u2019 We continue to treat people as if they might be infectious because the truth is we don\u2019t know.\u201d<\/p>\n Instead of mask-wearing, the White House has relied heavily on testing to prevent outbreaks. That, too, is problematic. \u201cMany White House officials have been feeling comfortable after receiving a negative test,\u201d Cevik said, \u201cbut maybe they don\u2019t necessarily understand or haven\u2019t been told the negative test doesn\u2019t give you 100 percent clearance.\u201d <\/p>\n As Vox\u2019s Brian Resnick reports, coronavirus tests can fail for a multiplicity of reasons \u2014 including improper swabbing or taking the test before someone has enough virus to test positive. This means anyone who encountered Trump, who wasn\u2019t wearing full personal protective equipment while Trump is infectious, could now be carrying the virus, even if they\u2019ve tested negative. According to guidelines, those people should be quarantining for 14 days, too.<\/p>\n If the White House wants to prevent more coronavirus infections, they\u2019ll have to change course. \u201cTesting on its own is not going to prevent onward transmission,\u201d Cevik said. But isolating \u2014 in addition to masks, contact tracing, social distancing, and testing \u2014 can.<\/p>\n Eliza Barclay contributed reporting to this story.<\/em><\/p>\n Correction, October 7: This article originally misattributed a quotation by Ilan Schwartz on the limits of advanced Covid-19 diagnostics to Sigal Yawetz. <\/p>\n \n \n