As an infectious disease epidemiologist who’s worked on pandemics for two decades, I’ve talked in recent days to journalists and health officials around the United States and from halfway around the world about how to stop the coronavirus. They all have the same questions: How many tests do we need? How should we use tests? For each case we know about, how many more cases are out there? What’s the best way to find undiagnosed cases? Should we do “active case finding,” which involves testing everyone who is mildly ill, then isolating known cases and quarantining and isolating their contacts? Instead – or in addition – should we implement intense social distancing, close schools and take other similar measures?
Everyone asks the same important, interrelated questions. In one respect, the answer is the same for all of them: We must vastly expand our testing capacity. No country has controlled transmission effectively without massive testing capacity. The United States currently has a sliver of the capacity we need, which is only a tiny fraction of that available in other countries. South Korea has performed over 320,000 tests – almost one for every 150 people. That is 30 times the testing per capita that we have done in the United States. Exceptional teams are racing to solve testing bottlenecks at local and state levels (Massachusetts is just one example), filling the vacuum left by the complete absence of federal leadership. Regulatory and technical hurdles accounted for early delays. Now that we’re past those, several shortages are getting in the way. We don’t have enough protective equipment for testers, nor swabs for sampling or reagents to extract genetic material from the virus. We don’t have enough physical test kits, or enough human power to run large-scale testing. The result is that we have no idea how many people are infected with the coronavirus, or how fast the virus is spreading.
For most of the other questions about strategy, the best answer depends on local conditions. Different parts of the world, and maybe even different parts of the country, are in very different situations. The best strategy depends critically on which stage of the outbreak you are in, how much testing is available. This is a subject infectious disease epidemiologists have been thinking about for years. My colleagues and I have been adapting our earlier peer-reviewed work to the present pandemic. One size does not fit all.
A few places – many of them islands, like Singapore and Taiwan – have so far kept the epidemic relatively under control. They found and tested most of the initial imported cases; they deployed a skilled public health workforce to isolate people with the virus and trace and quarantine their contacts; and they’ve managed to maintain a “containment” strategy to good effect. The same can be said of Hong Kong and New Zealand. Iceland has combined containment with massive testing of its population. So far, this strategy has worked, and in these places, it would be wise to keep to it unless evidence that it is failing starts to emerge.
Containment can work when there are few enough cases that the public health system is able to deal with them and their contacts, so that the workload is manageable, and when a large fraction of cases are tested and identified, so that preventing them from infecting anyone else dramatically reduces the total amount of transmission.
For jurisdictions like these, case-based interventions (isolation, contact tracing and quarantine) can be the centerpiece of the control strategy – because they are highly effective. It may be necessary to supplement these with broad social distancing measures, of the sort we have been emphasizing recently in the United States, to snuff out any unobserved chains of transmission that might get past public health authorities. Places like Singapore can afford to keep schools open – and more generally to impose less stringent social distancing measures – precisely because the case-based interventions are working.
But the situation in the United States right now is very different.
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SOURCE: The Washington Post, Marc Lipsitch