- Public health specialists, including Assistant Secretary for Health Adm. Brett Giroir, who leads the U.S. testing effort, have long emphasized that testing alone is not a public health intervention.
- The White House, however, has relied on a strategy known as screening, in which people without symptoms are tested frequently for the virus before being allowed on the premises.
- Trump and other administration officials have used frequent testing as a justification for why the president and his officials often don't need to wear masks or socially distance.
The White House has for months relied on frequent, rapid coronavirus testing to keep its officials and staff safe, but President Donald Trump's diagnosis shows how testing alone cannot stop the virus.
Public health specialists, including Assistant Secretary for Health Adm. Brett Giroir, who leads the U.S. testing effort, have long emphasized that testing alone is not a public health intervention. It should be implemented, they've said, alongside strategies like masking, social distancing, washing of hands and the quarantining of suspected patients.
The White House, however, has relied largely on the screening of all staff and visitors of the White House for the virus with a rapid turnaround test. Trump and other administration officials have used frequent testing as a justification for why the president and his officials often don't need to wear masks or socially distance.
"I put a mask on when I think I need it," Trump said Tuesday at the presidential debate. "Tonight, as an example, everybody's had a test and you've had social distancing and all of the things that you have to, but...I wear masks when needed."
Alex Azar, Secretary of the Department of Health and Human Services, doubled down on the president's comments even on Friday, after Trump announced he had tested positive.
"The first family and the protective aspect around the president is a different situation than the rest of us because of the protocols around the first family," Azar said at a congressional hearing when asked about the president and his family not wearing masks. He added that most Americans should follow all public health guidance, including mask wearing and social distancing.
While screening has caught some infected people without symptoms before they entered the White House, it's not a perfect way to keep the virus out and epidemiologists who spoke with CNBC said they're not surprised the virus has sneaked past the system.
"I don't think any experts recommend that you use medical screening tests as a replacement for social distancing, or masks, or other kinds of mitigation efforts," Dr. Ben Mazer, an anatomic and clinical pathologist at Johns Hopkins Hospital, said in a phone interview. "They all think this should be done in combination with masks, social distancing and all the other recommended measures."
Dr. Sadiya Khan, an epidemiologist at Northwestern University compared the White House's testing strategy to that of different sports leagues. Despite frequent and widescale testing, both Major League Baseball and the National Football League have seen infections among their ranks, she said. But the NBA, she added, has successfully kept the virus at bay by not only testing, but also keeping their players quarantined in the so-called bubble.
"Testing doesn't make you immune and testing doesn't eliminate the virus," she said. "No single strategy is probably ever going to be successful completely on its own."
The White House, in a statement to CNBC, said its procedures incorporate current CDC guidance and best practices both at the White House complex and while the president is traveling.
"In addition to encouraging social distancing, readily available hand sanitizer, regular deep cleaning of all work spaces, and recommended facial coverings, those in close proximity to the president continue to be tested for COVID-19 to ensure exposure is limited to the greatest extent possible," White House spokesman Judd Deere said.
Staffers, guests and reporters have all been required to be tested for the coronavirus with Abbott Laboratories' ID Now test before entering White House grounds. That test is a rapid molecular test that can produce results in as little as 15 minutes. But some epidemiologists have raised questions about the accuracy of the tests.
"This was not a surprise actually what happened here," Dr. Michael Osterholm of the University of Minnesota told CNBC. "I have been a fairly vocal public critic of the White House testing program using the antigen test as they were using it because in fact it is so insensitive. Up to half of the people who are infected could test negative by that test."
In a statement, Abbott spokesman Ross Darcy defended the accuracy of the ID Now tests and wished a speedy recovery to the president and first lady.
Justin Lessler, an epidemiologist at Johns Hopkins Bloomberg School of Public Health, called Abbott's ID Now an "imperfect test." He added that the tests can diagnose someone as negative even if they're infected, especially if they're early in their course of infection.
However, he added that the White House testing program did work to apparently identify the virus in the president early in the course of infection. That helps to cut off chains of transmission and potentially help in treatment, Lessler said.
In order to test staffers who could have been exposed to the president or other infected people in his orbit, the White House is turning to a new test, Abbott's BinaxNOW test, a senior White House official told CNBC's Kayla Tausche.
But that test test is currently only authorized by the Food and Drug Administration to test people who are displaying symptoms. When asked about the plan Pia MacDonald, an epidemiologist at the nonprofit RTI International, said the White House should use the more accurate PCR, or molecular, tests.
"I just know if I had been in the same room as the president, even wearing a mask, for 15 minutes or more, even 10 feet apart, I would want to go and get a very good test," she said. "I'd get the PCR diagnostic [which have] a better chance of actually picking it up."