[Update: This Perspective in the New England Journal of Medicine on False Negative Tests for SARS-CoV-2 Infection — Challenges and Implications was just published on June 5 2020, which adds a good perspective on this discussion. Dr Carlos del Rio, Emory University, commented on Twitter: “A very good perspective in @NEJM but it unfortunately fails to mention Pre-analytical problems, such as poor specimen collection, as major cause of “false negatives”.”]
As protests spread nationwide, public health experts have weighed in on how to reduce the risks of spreading COVID-19 while protesting. But with large groups converging, it is likely to come into contact with someone that is an asymptomatic carrier.
On Thursday, four days after leading a protest in downtown Athens for racial justice and against police violence, Commissioner Mariah Parker disclosed she had tested positive for COVID-19. She also urged others that had come in contact with her to get tested.
Multiple discussions on local Facebook groups referred to this fact and people also expressed doubts as to when the best time to get tested was.
Should everyone that attended the protest get tested? Only people that came into close contact with a confirmed case? Only those showing symptoms? And when is the best time to go get tested?
This same Thursday, the Minnesota Department of Health issued a recommendation through Twitter that “any Minnesotan who has attended a protest, vigil, or community clean-up get tested for #COVID19. If you start to feel sick, get tested right away. If you do not feel sick, get tested as soon as you can, but no later than 5-7 days after the event.” and also that “if the test is negative and you are worried you might have been exposed, get another test 12-14 days after the event, even if you do not feel sick.”
But we know that COVID-19 tests have high false negative rates, especially soon after exposure (on the day of symptom onset, which is day 5 on average, the probability of a false-negative in an infected person is around 38%, but this can vary widely). The best estimates show that the least number of false-negatives come when testing 8-10 days after exposure (around 20% probability of a false-negative at the minimum).
The Minnesota approach will mean that if a lot of people get tested only 5 days after being exposed there will be many false negative cases. At a population level this might be very helpful because any cases you catch will be less likely to infect others. However, for an individual it might not give them that much information, as false negative rates are still high 5 days after exposure.
It might also still be too soon for all those infected to have started showing symptoms, and the tests always have some false negatives. So any negative results from such a COVID-19 test need to be taken with a pinch of salt, and be coupled with risk-reducing behavior (such as wearing a mask, maintaining a distance from others, and frequent hand-washing). And a follow-up test might also be helpful if someone was close to a confirmed case.
When contacted the Georgia Department of Health did not have such recommendations but did say that “anyone who wants to be tested for COVID-19, regardless of symptoms, can schedule an appointment at one of our 140+ SPOCs around the state by calling their local health department. If people believe they’ve been in contact with someone positive for COVID-19, they should self-quarantine and monitor for symptoms, and seek medical treatment if needed.”
If people are able to self-isolate following protests for 14 days that would definitely be the first step to take. But many people won’t be able to do that, so risk mitigation and focusing on harm reduction, an approach strongly advocated by infectious disease epidemiologist Dr Julia Marcus, should be the priority. Whether someone decides to get tested early on to see if they can get a quick answer or decides to wait to get a more accurate reflection of the risk of being infected with COVID-19, it is important to understand what a test can and cannot tell you and continue to observe good infection control practices.
The Georgia Department of Health added that regarding the effects of the protests on the spread of the disease, “the incubation period for COVID-19 can be as long as 14 days, so it’s a little early to know what the increases might be. However, DPH will closely watch for increases from the events of the past week the same way we monitor for hotspots or increases from any large gatherings such as Memorial Day weekend.”
It is also important to remember with any discussion of the protests and the effects on COVID-19 transmission that while COVID-19 is a public health crisis so is police violence and systemic racism, as individual and organizations of public health experts have repeated over the last few days. A recent NPR article referred to this, saying that “the risks of congregating during a global pandemic shouldn’t keep people from protesting racism, according to dozens of public health and disease experts who signed an open letter in support of the protests.”
More information about testing and false-negatives: