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Who Should Get Tested For A New Disease?

Between May 6 and July 20, doctors in the United Kingdom confirmed 2,162 cases of monkeypox. Ninety-nine percent of those cases were men.1 That could be most reflective of who is contracting the virus. But it could also be partly because 80 percent of the people tested were men.

Public health officials have emphasized that the monkeypox outbreak is largely affecting men who have sex with men. That’s not incorrect. But there’s a side effect of that kind of framing: People who don’t fit into that category may think they can’t get monkeypox, might be afraid of what others will think of them if they contract it, or may even have trouble convincing a doctor to test themeven if they have symptoms of the disease. “You’ll never find [a disease] in a population you don’t test,” said Thomas Holland, a professor of infectious diseases at Duke University, who also sees patients at the University’s hospital.

This problem hampered U.S. public health officials during the initial stages of the COVID-19 pandemic, when tests for the illness were unavailable unless you’d recently traveled abroad, and the virus spread unchecked through communities believed to be uninfected. We know how that turned out.

Deciding who to test for a new — or newly ascendant — illness is a challenging paradox. Limiting testing isn’t always a bad idea and can even be necessary because of a lack of resources. But, sometimes, it is a bad idea. And it’s not always clear which side of that line you’re on until it’s too late. 

When medical experts are faced with deciding which patients should be tested for a new, scary illness, they have to ask themselves, “Is this gonna be more like Ebola, or more like COVID-19?” 

In 2014, when Ebola made a brief landfall in North America, and in the first months of 2020, when COVID-19 was brand new in the U.S., tests for either disease were a limited resource. In both cases, the public health community kept a tight rein on who could get tested. It took more than a fever and chills, said Brittany Kmush, a professor of public health at Syracuse University, since the symptoms of both diseases overlapped with other more benign illnesses. To be tested for either, patients needed an epidemiological connection to them — in particular, having recently visited countries where they were already known to exist.

“That worked pretty well for the Ebola outbreak,” Kmush told me. The protocol kept hospitals from being overwhelmed, caught the cases that truly needed isolating, and no significant spread went undetected. But the same wasn’t true with COVID-19. “I think with COVID, we really learned a lesson that we don’t always know what is going on,” she said.

But broad, open testing isn’t always the right choice. That did turn out to be necessary with COVID-19, Holland said, but early on there were a number of factors that made the strategy unworkable. Infamously, both tests and processing equipment were in short supply at the time, and getting results could take a week. In the meantime, he said, people waiting for results were kept at the hospital in isolation units visited only by staff wearing protective coverings and masks, which were themselves a limited resource.

Lots of hospital patients had symptoms that could have been COVID-19, he said. But, at that early stage, statistically speaking, Holland knew most of them didn’t have it. There was real danger in treating all those people as potential COVID-19 cases, not just the stress of unnecessary isolation and using up limited hospital space, but also from failing to diagnose what, if not COVID-19, was actually wrong with them.

“It was how I spent my days,” he said, deciding who got a COVID-19 test and who did not. “Those were some of the hardest conversations I’ve ever had professionally.”

But Holland and other experts I spoke also with see problems with how access to monkeypox testing has been restricted. Testing capacity for this new disease was limited early in the spring and summer, but it isn’t now, said Sandra Kemmerly, an infectious disease specialist in the New Orleans-based Ochsner Health System. And while monkeypox occurs primarily in men who have sex with men right now, it’s perfectly capable of infecting people outside that demographic.

The Centers for Disease Control and Prevention’s criteria for a probable monkeypox case includes having known contact with other monkeypox cases, being in contact with a community where it’s spreading (like men who have sex with men), or having recently traveled to a country where monkeypox is spreading. However, Kemmerly said the Ochsner Health System is encouraging doctors to expand their idea of who might be a potential case — to test based on symptoms rather than on contact with a high-risk community.

“One thing that’s been taught to us through HIV and repeated in COVID is if you have very narrow criteria for testing you’ll miss cases,” Kemmerly said. On the other hand, Holland said, wider testing needs to be balanced with the potential for false positives and the risk of informing someone that they have a disease that’s been heavily stigmatized when they actually don’t. 

The good news is that doctors say they’ve learned some lessons from past pandemics. For example, the experience of COVID-19 seems to have taught the public health community the importance of producing more tests and quickly enabling more places to process them. Kemmerly was impressed with how quickly the CDC made partnerships with commercial labs and increased testing capacity on monkeypox. 

Holland also found it important that testing for monkeypox has been expanded to a wider variety of medical facilities people are likely to already frequent — like dermatologists and sexual health clinics. 

And the COVID-19 experience has also made wastewater testing for communicable diseases something more local public health systems have familiarity with and infrastructure for, Kmush said. (Some areas of California are already using it to test for monkeypox.) That would really help because even if men continue to make up the bulk of individual test-takers, wastewater can help determine whether the virus has spread further.

But maybe the most important lesson for the future, Kemmerly said, is that you can’t just pick one position — test broadly or test narrowly — and expect to stick with that for the long haul. “As new diseases emerge and different modes of transmission become more common, we have to be ready to more rapidly reevaluate our criteria for testing,” she said. When all the options are imperfect, the worst thing you can do is refuse to change. 


  1. Where gender information was available.

Maggie Koerth was a senior reporter for FiveThirtyEight.


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