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Five charts that show why people are worried about another COVID-19 surge in Mass.

At Mass General Hospital, hazmat-suited EMTs wheel a patient into the emergency room in April.Stan Grossfeld/ Globe Staff

After a sudden jump Thursday, Massachusetts coronavirus cases have been maintaining levels we haven’t seen in months, raising concern among experts that the state might need to consider rolling back some parts of its reopening process.

Here are five charts that will show you why people are worried:

Let’s start with the high-tech. The chart below shows results from tests for traces of the deadly virus in waste water at the Deer Island treatment plant. It shows that traces are rising sharply in communities both on the northern and southern side of the Massachusetts Water Resources Authority system. Officials started the testing in the hope that the pilot project could serve as an early warning signal for outbreaks of the virus.


The chart shows the state controlling the virus in the summer and then a gradual rise since, a pattern visible in other data from the state. In recent days, the tests showed a sharp jump.

“Every day, I stare at this wastewater data from Massachusetts and get more and more concerned,” Dr. Ashish Jha, dean of the Brown University School of Public Health, said in a tweet over the weekend.

Now, back to an old familiar. This chart shows the daily number of coronavirus cases announced and the seven-day trend of those cases, which on Sunday reached 925. Only a month before, the seven-day average was 392.

The number of positive tests for coronavirus is rising even as the number of tests administered has remained relatively stable. This is reflected in a rising positivity rate.

This chart shows two ways the state has calculated the positivity rate. The first method, used to produce a rate that is highlighted in the state’s closely-watched daily data dashboard, is to divide the total number of positive tests over a week’s time by the total number of tests administered.


The state also offers a different method: Divide the total number of positive cases by the number of people tested for the first time. That number, which does not include repeat negative tests such as those for college students undergoing routine testing, is rising more dramatically. The state offers only a daily percentage in its dashboard, but the Globe has been able to calculate the seven-day average from data files provided by the state. Some experts say the number is a better measure of the pandemic.

Some coronavirus cases lead to hospitalizations and some of those cases eventually lead to deaths. This chart shows that hospitalizations have been gradually rising, a potential sign of trouble ahead.

Finally, the recent data suggesting that there’s reason to worry in Massachusetts comes at a time when experts are issuing dire warnings that the colder weather will lead to more cases and deaths — and data show the virus surging in other areas of the country, the onset of a third national surge.

Here’s a chart showing the initial national surge in the spring, the second surge in the summer that was driven by other states while Massachusetts squelched the virus, and the third surge that is now underway.

The crucial question is: Will Massachusetts cases start rising like the national numbers or will the state be able to put the brakes on?

John Hilliard and Dasia Moore of the Globe staff contributed to this report.


Martin finucane can be reached at martin.finucane@globe.com.