Massachusetts' new COVID-19 dashboard is an easy, color-coded way to see which communities are experiencing spikes in positive test results.
But the so-called "red" communities can often have vastly different case numbers.
"So, if you have 10 cases in a small community, that's going to give you a much higher rate of infection than 10 cases in a large city," said Dr. Daniel Karitzkes, the chief of the Infectious Diseases Division at Brigham and Women's Hospital.
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He says epidemiologists like to work with rates of infection to get a clearer picture of the potential of exposure in each community.
"We have to remember these rates change over time, and we can expect fluctuations where there may be bumps and valleys," Karitzkes said.
Those fluctuations can be bigger with smaller numbers to work with, like in Sutton, with a population of under 10,000 people.
And that can be tricky when basing decisions on school reopening plans partly on community coronavirus rates.
"I think the superintendents really do need to take into account the rate of infections, not just the total number of infections," said Karitzkes.
"We will work with the local public health department to determine if we can stay in school," said Theodore Friend, superintendent of Sutton Public Schools. "With so few cases, we should be able to make an informed decision for our students and staff."
"No individual tool is going to give you the complete picture, and no particular tool is precise or fool-proof, so we really need to look at the total information available," Karitzkes said.
In Sutton, there are currently two weeks of professional development for teachers before students are scheduled to start in a hybrid model Sept. 14.