An ongoing dialogue on HIV/AIDS, infectious diseases,
October 4th, 2020
Does the White House Outbreak Invalidate the Strategy of Frequent Testing for COVID-19 Control?
As I’ve written here many times, I’m hopeful that frequent, inexpensive, rapid home testing for COVID-19 will help us climb out of this pandemic mess.
Let’s name it the Mina Frequent Testing Plan, after my indefatigable colleague Dr. Michael Mina who has championed it for months — most recently in a perspective published in the New England Journal of Medicine.
For the Rip Van Winkles out there, here are the basics of this approach:
- Much of the community transmission of SARS-CoV-2 comes from people who don’t know they are infectious since they have no or few symptoms.
- Testing them using standard PCR tests is impractical — too slow, expensive, and difficult to access.
- Scientists and companies have collaborated to develop simple paper-based rapid tests done on saliva samples.
- Results return in 15-30 minutes and require no special instruments for interpretation — analogous to home pregnancy or HIV tests.
- Produced at scale, the tests are cheap and readily available — $1-5 each.
- These tests pick up some people who have high levels of infectious virus but are either asymptomatic or presymptomatic — hence potentially contagious to others but otherwise unaware themselves. Now, none of these people are being detected.
- Once they have a positive test, they isolate at home — they don’t go to work or school. Tests would be confirmed using standard PCR.
- Individuals can also buy them for use at home.
- Schools, hospitals, nursing homes, food service companies, places of worship, and others can purchase them in bulk, with requirements for a negative test (even better, a series of negative tests over the previous several days) for entry.
The strategy has a growing number of advocates across the medical, scientific, and public health fields — including the FDA — which is exciting. Here’s a short white paper on the topic many of us have helped draft, with a focus on testing in schools.
These negative views certainly raise important concerns. I worry in particular about false positives — they will be inevitable when doing high-volume testing on a low-prevalence population.
Now, we have a president who acquired COVID-19 despite the fact that he and those who surround him are tested often.
How did this happen? Is this the death knell of the Mina Frequent Testing Plan?
The obvious first explanation is that no test is perfect. The rapid antigen tests used by the White House will miss some people who are infectious. Of particular concern are those who get tested only once, right before meeting the president.
The math is simple — if you increase the number of visitors, you increase the chance that at least one person with infection will escape detection with a single rapid test.
Remember, one strength of the Mina Frequent Testing Plan is just that — it’s frequent! People who test negative in the early phase of infection will test positive with tomorrow’s or the next day’s test based on the kinetics of viral replication in someone who has just come down with the disease.
From Mina’s NEJM piece, here are those viral trajectories — a person with a negative test in the morning could potentially be infectious shortly thereafter:
With the many visitors to the White House on Saturday, September 26 — the day the president announced the nomination of Judge Amy Coney Barrett to the Supreme Court — only a single rapid test granted them access to the event, mask-free.
Also, let’s remember that testing won’t give us a free pass to behave as if we were living in the Before Times, again because testing isn’t perfect. Certain activities facilitate spread of the virus — crowds, close conversations, poor ventilation.
How about this for an example?
At least 7 people who attended ACB's nomination ceremony in the Rose Garden on Sep. 26 have since tested positive for coronavirus. But experts say the more risky time spent that day was at a reception inside the White House. Here are some scenes. https://t.co/mTsZsxmSfy
— Christiaan Triebert (@trbrtc) October 3, 2020
Double ouch! Watching that video makes most of us ID clinicians feel like we’re living on another planet. Suspect many of you readers feel the same!
In summary, let me quote my Boston ID colleague Dr. Roby Bhattacharyya, who wisely wrote:
People tap-dancing prematurely on the grave of rapid testing should reflect on how remarkable it is that for people behaving this way all year, indoors and out, in a place with countless thousands of visitors, it took until October for a superspreading event to happen. Test more.
So yes, the Mina Frequent Testing plan lives on — even if the track record of keeping the president free of the virus does not.
Which teaches us more about the limits and vagaries of human behavior than it does the limits of testing, doesn’t it?