A member of the National Guard assisting at a COVID-19 mobile testing location fills out paperwork for a motorist arriving for a test Tuesday, Dec. 1, 2020, in Auburn, Maine. Credit: Robert F. Bukaty / AP

It’s less and less clear how Mainers are getting sick with the coronavirus, as record numbers of new infections have thwarted the ability of state disease detectives to map out exactly how the virus is spreading.

The difficulty of closely tracking how people caught the coronavirus is yet another sign of how much more it is circulating in Maine now, even compared to just a few weeks ago, and beginning to overwhelm various parts of the state’s response.

State health officials have highlighted some trends they’ve seen as they investigate the new swell of cases, including that private gatherings are increasingly taking place indoors and without masks amid colder weather, and that a smaller portion of new cases can now be attributed to large outbreaks at nursing homes and factories, or to smaller outbreaks in group homes.

Investigators so far have attributed a fifth of November’s 5,311 confirmed cases, or 1,155, to known outbreaks, and an even smaller slice of December’s, although the numbers for both months could grow as new links are found, according to Maine CDC spokesperson Robert Long.

That suggests the virus is increasingly spreading among people going about their daily lives — whether shopping or visiting relatives — in a pattern known as “community transmission.”

Yet it’s growing harder for state investigators to tease out exactly how that community transmission is happening, especially given that already significant case volumes have been multiplying for weeks, creating many more possible avenues of infection. In workplaces and venues that have had outbreaks, it’s no longer so clear whether workers passed the virus to each other on the job, or whether they all just caught it at the same time from friends and family out in the community.

“The chains of transmission are blurry at this point,” Maine CDC Director Nirav Shah said this week. “Initially in COVID, across the country, it was a series of straight lines, dots that we could connect. Now, it’s a bowl of spaghetti, and that’s the definition of community transmission.”

Community transmission has been blurring the picture “for weeks and weeks and weeks” now, Shah noted.

As community transmission leads to ever higher numbers of cases, it has had the secondary effect of swamping the detectives whose job is to investigate the source of each infection and identify people who have come in contact with people who tested positive. As a result, the state had a backlog of 4,000 new positive test results it still hadn’t fully sorted through at the start of this week.

TRACKING THE CORONAVIRUS IN MAINE

In part due to how much time it would take to go through that backlog to determine the actual number of new cases — some are duplicate results for the same person — the Maine CDC shifted its approach at the start of this week: its investigators will no longer try to determine the origins of all confirmed cases of COVID-19, but just those that have sickened people in one of several high-risk groups, including medical workers, nursing home residents and children.

While that “extremely difficult” decision was meant to protect those vulnerable populations, according to Shah, it means that the state will no longer try to track the origin of 40 to 60 percent of new cases.

Although its investigators are busy tracking the spread of COVID-19, Maine CDC has not been able to provide clear data to quantify just how much of the new spread is coming from different settings, such as private gatherings at people’s homes or people going out to restaurants at night, even as Gov. Janet Mills recently extended a 9 p.m. curfew for businesses.

A few states — including Minnesota, Massachusetts and Vermont — do appear to publicly track and report the types of settings where people may have been exposed to the virus, at least in cases tied to outbreaks. But many do not systematically collect those statistics, according to the New York Times.

The Maine CDC is not currently able to provide a breakdown of the types of settings where infected residents are thought to have been exposed to the virus, according to Long, the agency spokesperson. He said it might be able to compile that information after the public health “emergency abates, when epidemiologists have had a chance to review and validate data from case investigations.”

The agency has provided the average number of close contacts infected people have reported to state investigators — just 3.5 for the first seven-and-a-half months of the pandemic, but 5.8 in October alone, suggesting people were socializing more frequently this fall.

And during late October and increasingly in November, investigators noticed a trend of infected people reporting that the “only place that I have been is to my friend’s house last week or my brother’s house last Sunday, or having some friends over to watch the game,” according to Shah. There appeared to be a corresponding lack of face mask wearing by the people at those indoor gatherings, Shah said, although he doesn’t “have data to prove it.”

Federal health officials overseeing the national pandemic response, including top infectious disease expert Dr. Anthony Fauci, have also pointed to private social gatherings as a driver of new outbreaks this fall, raising concern that holidays such as Thanksgiving and Christmas could worsen the new surge in cases.

Although it has become “very hard” for state investigators to chart exactly how the coronavirus is spreading now that it is rampant across every part of Maine, Shah said that he still sees “value” in the effort.

“They allow us to see the light of potential outbreaks, which is something that we can intervene on really quickly, as well as communicating with folks who have tested positive so that we can give them advice on what to do,” he said. “So we’re not giving up.”

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