Since the start of the Covid-19 pandemic, there has been endless discussion on how to protect the public. In the beginning, we didn’t know much about this new virus. Now, many months later, our scientists and medical experts understand much more about how the virus is transmitted, how deadly it can be, and how patients can be treated. Still, a vaccine is still a long way off and the spread of new cases continues around the country. Earlier this month schools began to open across the country, which is great for education and for working families with kids – but which may reignite the spread. While some people talk about the idea of another lockdown, others doubt that American businesses can survive until the end of the year.
As it turns out, in all this chaos there is something that we missed — a proven method that to fight Covid-19.
Last January scientists created a high-quality test for an active viral infection. Since then we have managed to test millions of Americans and our testing capacity continues to grow. However, efforts to test at the necessary level in the United States have fallen short. Paul Romer, the Nobel Prize-winning economist, in talks, papers and full-page ads in major papers, calculates that everyone in the US should be tested every two weeks in order to vigorously reopen the country. Unfortunately, Romer’s solution requires that we test about 30 million people per day in the US. For comparison, we tested only about 13 million people between March and May.
So how can we ramp up testing and reopen the country? Well as it turns out the answer is math.
How can math help fight a virus?
A statistician by the name of David Donoho gave a presentation at the 2020 SIAM Conference on Mathematics of Data Science in May in which he reviewed mathematical and statistical methods that could be used to ramp up testing. These ideas came from research being done around the world on how to combat Covid19, using methods that worked with other diseases. During that talk, he highlighted two papers that mentioned the idea of multiplexing patient test samples to increase testing capacity up to 10 fold, without new testing machines.
I had the opportunity to interview David Donoho about this topic and he told me that the ideas are well-proven in past epidemics and that “Today, research is going on all around the world to verify that those ideas can be used in successfully, with the Covid-19 tests specifically. The math is so general and robust, that, once we know it applies to tests like these, then we know the scale up will work.“
Read more about that research here.
How does it work?
Right now we are using one test for one person. Seems like a logical way to test people but if we are smart about it we can test several people at once. Ultimately, we can test up to 10 times more people while using only the machines and operators we have now.
Imagine we process 100 people in this way. First samples have to be collected from each person being tested. Next, we divide each person’s sample into three; their sample will be tested three different times. Each of those three tests will combine samples from thirty different people; when such a test comes back positive, we know that someone among those thirty is infected. Depending on which pools come back negative or positive a mathematical algorithm can decide which individuals have Covid-19 and which do not. The math problem is similar to a logic puzzle or sudoku.
This approach is often referred to as ‘pooled testing’. It requires that the puzzle be properly set up and then properly solved. That may seem difficult or time-consuming to people like me who take all day to solve a sudoku puzzle. However, in the world of computer programing, these puzzles are not hard at all. With a simple program, you could solve an entire sudoku book in microseconds.
Testing is only the beginning
In order to combat the spread of the virus, testing will take us farther than you might first think. The battle plan is actually fairly simple. Those that test positive will have to self-quarantine for two weeks (and seek medical attention). When that’s done, people would only return to normal life after testing negative. This would remove a large number of sick people from the general population and therefore stop the spread.
The FDA has recognized the value of this approach – it gave approval to the idea in June. Some large organizations are using it: Cornell university is planning a full re-opening this fall, with every student tested every 5 days – and they say they will rely on pooled testing.
For now, it seems the plan in most of the country is to just reopen everything and keep our fingers crossed.