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Now that the coronavirus has been circulating around Maine for more than two months, the ever-growing mass of numbers, anecdotes and other information about the pandemic may be dizzying to anyone without a very strong interest in biology or disease surveillance.
So the BDN has reached out to a few public experts for their advice on the best metrics to pay attention to that demonstrate the severity of the coronavirus pandemic.
For Mainers, the good news is that the state is already keeping track of those figures and expects to make quick progress on one of them through a new partnership with the company IDEXX to greatly expand testing for the virus.
The bad news is that even if the state ramps up testing and brings the number of known active cases down over the coming weeks, even the best surveillance and data won’t be enough to stop the virus in its tracks until adequate vaccines or treatments can be developed.
Until then, the threat of new outbreaks of COVID-19 — the disease caused by the virus — will remain, along with the deaths and suffering that accompany them. As a result, officials may reimpose restrictions if the illness starts to make a comeback.
Here are some of the most important measures to watch.
While the state’s overall number of coronavirus cases is important (see next section), that measure is only as good as the surveillance behind it. That’s why all three experts interviewed for this article said that testing capacity is a critical factor affecting how well states can quickly identify and isolate new cases of the virus going forward.
Testing capacity can be assessed in at least two ways. One is the overall volume of daily testing that the state is doing, according to Samuel Scarpino, an epidemiologist at Northeastern University in Boston. It was in part through widespread testing that countries such as South Korea and Singapore were able to get their own COVID-19 cases under control, Scarpino said.
As of late April, an analysis by the Harvard Global Health Institute found that Maine needed to conduct at least 583 tests per day to safely reopen its economy, but that it was only doing an average of 406.
However, beginning next week, the state will be able to greatly surpass that benchmark through its partnership with IDEXX, which will allow the state’s testing laboratory to triple its capacity and complete an average of 1,000 tests per day, according to Director Nirav Shah of the Maine Center for Disease Control and Prevention. That’s in addition to the testing that private labs are able to complete.
Another way to assess whether states are doing enough surveillance is by calculating what percentage of its COVID-19 test results are positive, according to Eleanor Murray, an epidemiologist at Boston University.
If that rate is 10 percent or higher, it means that states are probably not doing enough testing and limiting who can get tested based on criteria such as the severity of their symptoms, according to Murray. But if it’s well below 10 percent, it means states have the resources to test a wider array of people even if their risk of having the disease is somewhat lower.
Last week, Shah said that Maine’s positive test rate was around 5.9 percent, but that he hopes the new testing will bring that down to 2 percent.
However, in both cases, Murray and Scarpino cautioned that it will be important to watch how those numbers are changing over a period of weeks, rather than focus on where they are at any given time.
Another important measure is how many new cases of the virus Maine is reporting each day.
Again, the trend in that number is more important than a single point in time, according to Dr. C. Robert Horsburgh Jr., a professor of epidemiology at Boston University. Its reliability also depends on states having enough testing capacity.
If adequate testing shows that the number has been steadily dropping for at least two weeks and it has reached a low enough level, then a state can probably start to safely reopen its economy, he said.
While Maine’s day-to-day counts have varied, the state has seen little movement in new case numbers over the past two weeks when the numbers are presented as a moving average of the last seven days of new cases, according to Maine CDC data. For almost two weeks, that figure — which smooths out day-to-day fluctuations — has shown the state averaging 26 to 37 new cases per day.
The highest number of new cases in a single day, 76, was reported on May 7, largely driven by widespread testing at a Portland poultry-processing plant and a Westbrook long-term care facility that had outbreaks, but it hasn’t risen above 50 since then.
Now that Maine is preparing to expand its testing and loosen restrictions on which patients are tested for the disease, Horsburgh said that it will probably report an uptick in COVID-19 cases. Yet once that happens, it will give a more accurate picture of the virus’ trajectory in the coming weeks.
He warned that the accuracy of the overall case numbers will be all the more important if Maine starts reopening sections of its economy to out-of-state tourists, who currently are required to quarantine for 14 days once entering the state.
“There might be a bump in cases with wider testing,” he said. “Then you should start to see real decreases, and if not, that’s not good.”
Hospitalizations and antibodies
While testing capacity and new virus cases provide some of the simplest evidence of the pandemic’s spread, the experts pointed to a few other key numbers to watch.
As hospitals start to resume non-emergency services that were postponed during the surge of COVID-19 cases, Scarpino said the state should continue to track how many patients are hospitalized with the infection and how many intensive care unit beds are available in case there is a resurgence. So far, the state’s hospitals have been far from overrun with virus cases.
Both Scarpino and Murray also said that it will eventually be important to start tracking what portion of the population has developed antibodies against the coronavirus, which could suggest how many people have already been infected and may have immunity. More research is still needed to develop accurate antibody tests and determine how long COVID-19 patients are immune from catching it again, Murray said.
Watch: Why Maine is tracking number of tests instead of people tested