A fresh analysis of the numbers behind the coronavirus outbreak suggests that it’s reached the point where more intensive testing and social distancing will help far more than bans on travel.
Travel restrictions have come to the fore over the past day or so: During an address on Wednesday night, President Donald Trump announced that he was banning most travel by non-U.S. residents coming from 26 European countries, including Germany and France but not including Britain and Ireland.
Today, Trump said he’d also consider banning domestic travel to places like Washington state and California “if an area gets too hot.”
Such strategies led Trevor Bedford, an epidemiologist at Seattle’s Fred Hutchinson Cancer Research Center, to run the numbers for likely infections from abroad as well as from community transmission of the SARS-CoV-2 coronavirus.
You can check out Bedford’s Twitter thread for the back-of-the-envelope calculations, but the bottom line is that he estimates roughly 100 new infections would be introduced to the U.S. by European travelers every day. That compares with roughly 1,800 new infections per day passed along by people already in the U.S.
“This is a ratio of 18 to 1 for the number of new infections generated within the USA vs. infections brought in from Europe,” Bedford noted.
Those figures assume that there are currently 6,500 cases in the U.S. now, and that the number will double in the next week. That’s much lower than public health agencies’ tally of confirmed cases nationwide (which currently amounts to more than 1,300). Why? It’s because an analysis of evolutionary changes in the virus over time, conducted by Bedford and his colleagues with the Seattle Flu Study, suggests that most cases haven’t yet been confirmed.
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And why is that? The main reason is that so few Americans have been tested for the virus. Due to problems with getting the lab-test pipeline up and running in the United States, relatively few coronavirus tests have been run nationwide. The Centers for Disease Control and Prevention says only about 11,000 specimens have been tested at its labs and at public health labs over the past two months. Roughly 11 percent of the tests come back positive.
In Washington state, the Department of Health says its public health lab is currently capable of running 200 tests a day, and it plans to raise that figure to 400 a day. The University of Washington’s Virology Lab (which isn’t included in the CDC’s figures) joined the testing effort last week. It’s now testing up to 1,300 specimens a day, has enough capacity to do 2,000 to 2,500 specimens, and aims to raise that daily capacity to 5,000.
That kind of capacity will be needed if the Bill & Melinda Gates Foundation follows through on its plan to make at-home testing available, following the model set by the Seattle Flu Study for tracking influenza outbreaks.
During the early stages of an epidemic, limits on travel can make a big difference in how infection spreads. But at this stage of the game, Bedford argued that testing should be a bigger concern than travel. “I believe the focus needs to be on testing and case finding in the US to slow transmission here,” he tweeted. “Introductions through air travel are likely to have a more minor impact at this point.”
In contrast, President Trump downplayed the testing issue during today’s White House press availability with Irish Prime Minister Leo Varadkar.
“They have a million tests out now,” Trump said. “Over the next few days, they’re going to have 4 million tests out. And frankly, the testing has been going very smooth. If you go to the right agency, if you go to the right area, you get the test.”
Reports from the field, however, suggest that the testing effort has been anything but smooth. “The system is not really geared to what we need right now,” Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, acknowledged today during a congressional hearing. “It is a failing. Let’s admit it.”
Both of the remaining Democratic presidential candidates, Joe Biden and Bernie Sanders, advocated a heightened focus on free testing in statements that they delivered today on the coronavirus outbreak. Biden called for at least 10 mobile testing labs to be set up in every state, and advocated the establishment of drive-through testing centers like the station that UW Medicine set up in Seattle.
Knowing who has the virus makes a big difference in targeting the response to the COVID-19 outbreak. Many point to South Korea, where health officials have been running nearly 20,000 tests a day and are reporting a slowdown in the number of new cases.
But more tests alone aren’t enough. In an op-ed column written for The Seattle Times, John Lynch of Harborview Medical Center and Karin Huster of Doctors Without Borders stress that it’s also important to take advantage of social distancing and other strategies, including toughing it out if you can:
“As we ramp up our testing capacity and are able to test more sick folks, more and more cases will be identified. But having every sick person visit the emergency department to be tested and having all positive cases hospitalized — including those who would likely get better on their own — will quickly overwhelm our health-care system and risk its collapse. It will undoubtedly lead to diverting care away from patients who will be most at risk to develop severe forms of disease. This will no doubt lead to worse patient outcomes, additional work for hospitals and increased risk for health-care workers.
“Testing is no doubt a critical part of the response, but it is not the answer — reducing new infections is.
“And that is achieved by keeping sick people away from healthy people. Asking people to go to emergency rooms that are often busy and full of at-risk individuals is not a good idea. But having access to these tests, like we do at the University of Washington, allows us to identify infection in those at risk of disease progression, such as those over age 60 or people with heart disease. Staying home when you are doing well and have little risk for disease progression is the right thing to do. As well, leveraging tools like telehealth can also help to support people to remain at home while also still having access to their health-care providers at any time.”
