New CDC Covid Testing Guidelines Have It Backward
(Bloomberg Opinion) -- At least so far, the two most glaring failures of the U.S. response to the pandemic are in testing and public communication. Both came together this week when the CDC changed its testing guidelines in a way that had public health scientists baffled.
The new guidelines say people who don’t have symptoms of Covid-19 don’t need to be tested — even if they think they were exposed. “CDC is driving us all crazy,” says Barry Bloom, a professor of public health at Harvard. “This just makes absolutely no sense.”
You don’t have to be a scientist to see this as bizarre, after mass fear of asymptomatic spread caused millions to be shut up in our homes last spring, and remains the impetus behind mask mandates and other restrictions that treat all of us as potentially contagious no matter how healthy we feel.
The change also comes at a time when the technology exists to start scaling up Covid-19 tests that are cheap, painless and quick. Massive-scale, regular testing was the way many experts envisioned a return to normal life after all the lockdowns. That way, the small fraction of people who actually have an active infection could be quarantined, and the rest could live with much more confidence and freedom in the long months it could take to achieve widespread immunity through a vaccine. While the public has been blamed for being too impatient to stay locked down longer, the real blame lies with those who didn’t use the time we bought them to prepare a testing strategy and communicate it clearly.
Take the new CDC guidelines. “If you look at what they say, there are a bunch of weird contradictory guidelines,” says Harvard epidemiology professor William Hanage. The CDC is saying they don’t advise you to get a test, but you might be advised to get a test. It’s left up to individuals to decide, he says.
Worse still, the test technology we’ve employed is the wrong one to stem the infections. The technique, known as PCR, is accurate but takes too long to get results — a few days at best and several weeks at worst.
By then, the results might be almost worthless for identifying clusters or contacts early enough to prevent future outbreaks. Those who are positive have already spread the disease to most of the people they were likely to give it to. “It’s all about speed and speed is one thing we don’t spend enough time talking about,” says Hanage.
Even with the wait, though, experts say you should get tested if you were exposed to a known or suspected case — whether or not you feel feel sick. And ideally, people who work in healthcare, nursing homes and prisons should be able to get routine testing.
Speeding up the process would undoubtedly make all of this much more helpful. And a number of existing tests can deliver results in minutes. They don’t have to be sent to central labs to be processed but work more like home pregnancy tests. If those could become widely available, then many more people could be tested routinely, and even those without high-risk jobs could take an instant test before going to a restaurant or visiting friends and relatives.
Bloom says the advent of do-it-yourself testing will give the public a much-needed sense of control. Quicker test results can also help scientists understand how the disease is spreading. In Japan, Iceland and other countries with a more coherent testing strategy, contact tracing goes backwards as well as forwards. That is, if a person tests positive, public health workers would find out not just who they might have passed the disease to, but where they might have gotten it, and who else got it from the same source.
This is particularly likely to help contain Covid-19, says Hanage, because many cases don’t transmit to anyone, but a few give it to many in so-called superspreading events. A recently released study he co-authored used genetic fingerprinting of the virus to examine the outbreak that happened at a meeting of Biogen executives in Boston in late February. They found evidence that this superspreading event seeded about a third of all cases seen across the state, including several hundred in a homeless shelter.
Many of these cases could have been avoided had the outbreak been identified earlier. In Japan, he says, by working fast, a so-called cluster-busting approach has helped keep the disease levels low.
The big hurdle to getting faster testing is FDA approval. A number of small biotechnology companies have been given NIH grants to develop and scale up such tests, but some are not quite as accurate as the standard PCR test.
Or at least that’s the perception. PCR tests will give a positive result if people still carry traces of the genetic material of the virus long after infection, even if they are no longer capable of transmitting the virus to others. The quicker tests might be just as good at detecting people who are capable of seeding new clusters of disease — people who are carrying active virus rather than just remnants or fragments.
But FDA rules won’t allow approval of any test that’s less sensitive than the current standard, even if, in a practical sense, it’s a vast improvement. Those rules can be important for keeping bad drugs and diagnostics off the market, but in this case the criteria could be expanded as to what constitutes a superior test. With U.S. deaths crossing 180,000, a faster, less-accurate test might be just as valuable as a slower, more-accurate one. (One 15-minute test did demonstrate enough accuracy to be granted approval for emergency use – a $5 test kit developed by Abbott Laboratories. The U.S. government bought up most of the supply for $750 million.)
It’s becoming clear that there will be no single savior, but we’ll make progress against the pandemic through a combination of vaccines, better treatment, better understanding of how the disease spreads. Faster testing, though, has the potential to make the most dramatic improvement in the shortest time. The CDC should be doing all it can to encourage more and faster testing — not standing in the way.
This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.
Faye Flam is a Bloomberg Opinion columnist. She has written for the Economist, the New York Times, the Washington Post, Psychology Today, Science and other publications. She has a degree in geophysics from the California Institute of Technology.
©2020 Bloomberg L.P.