By Nick Giovanni

BOSTON (CBS) – Local epidemiologists are cautiously optimistic that the peak of the latest COVID surge may be behind us in Massachusetts, as wastewater shows a decreased presence of the virus in wastewater.

Samples are taken at the Deer Island Treatment Plant three times a week. The wastewater tested flows in from 43 communities around Boston. Testing detects the virus from people who have symptoms and from people who don’t.

In early December, the levels of COVID in wastewater began to go up, indicating the current surge was coming. But this week, the numbers are trending in the opposite direction.

“I was very encouraged by the downtrend, because it wasn’t just one day. It was actually several days in a row,” said Dr. Paul Sax, professor of medicine at Brigham and Women’s Hospital and Harvard Medical School.

Sax has been following wastewater data closely over the course of the pandemic as an indicator of just how prevalent COVID is in the community.

He said he is “cautiously optimistic” tracking the downward trend over the last several days.

“It’s been a substantial drop,” Sax said. “But just to remind you, it had increased to levels higher than we’ve ever seen before. So we’re still at a level that’s, believe it or not, even higher than it was last winter.”

Sax said if the trend continues, we should see case numbers dropping in a matter of days, possibly within a week.

Massachusetts has seen the number of breakthrough COVID cases nearly double for three straight weeks. This week, 86,466 new cases were reported in vaccinated individuals, up from 45,029 last week. Three weeks ago, there were 20,247 breakthrough cases.

“We still have a ways to go,” Sax said. “I cannot stress enough there’s plenty of COVID-19 out there even though this recent wastewater data is encouraging.”

Dr. Mark Siedner from Massachusetts General Hospital noted that we have seen peaks fall before, only to go back up again.

Health officials stress it is still critical to continue social distancing, and get vaccinated against COVID-19.

Nick Giovanni