The Big Moose Inn, left, and Tri Town Baptist Church. Credit: Linda Coan O'Kresik | BDN

Earlier this summer, Maine’s top public health official offered some advice for any young people who might have been thinking it was safe to hold a large party or get-together.

While they might feel safe to do so, Nirav Shah said, such gatherings could result in them catching COVID-19 and spreading the disease to their parents, grandparents or others with less robust immune systems.

When Shah broadcast that warning on July 30, Maine hadn’t traced any outbreaks to house parties or large social gatherings, although that kind of transmission was happening in many other states that had already loosened their coronavirus restrictions on bars, night clubs and gatherings.

“We haven’t identified a singular one yet,” said Shah, who heads the Maine Center for Disease Control and Prevention.

But just a week later, a young couple got married at a church in East Millinocket. Afterward, they celebrated the milestone with a 62-person dinner at an inn outside Baxter State Park.

Now, after a summer in which Maine controlled the coronavirus better than almost every other state, that couple’s fateful decision has spawned the state’s most far-reaching outbreak of COVID-19 yet.

It has infected at least 123 people and caused secondary outbreaks at a rehabilitation center in Madison and, more than 200 miles to the south, at the York County Jail in Alfred. One woman who did not attend the wedding has now died from the disease.

So far, the outbreak has not erased Maine’s progress in flattening the COVID-19 curve. Despite recent growth in daily case numbers, Maine’s infection rate throughout the pandemic exceeds only that of Vermont. But the wedding outbreak has caused a growing number of ripple effects, including many hours of work by state health investigators who must trace the spread of the disease, a delayed opening for schools in the Millinocket area and the state’s reassessment of whether it’s safe for schools in Penobscot and York counties to reopen full-time in person.

It has also created fear in the Katahdin region, which had seen few coronavirus cases in recent months. Following the outbreak, East Millinocket’s infection rate — the number of cases for every 1,000 residents — shot to fourth in the state, according to the state’s town-by-town case data. As of Sunday, its rate was 11.7 cases for every 1,000 residents. Medway, which had an earlier wave of 12 cases in the spring, now has the seventh highest rate in the state.

On a deeper level, the outbreak also has provided Mainers with a reminder of the rapid way in which COVID-19 can spread, even between people who don’t show any symptoms. During the early part of the pandemic, the most dramatic examples of that spread came in nursing homes, homeless shelters and other congregate living settings.

Now, the state has a sobering example of how the same rules can apply when people get together for more festive reasons — and how it can spread even when no one feels sick.

Before the wedding guests entered the Big Moose Inn — the Millinocket Lake venue which hosted the reception on Aug. 7 — they all were given temperature checks that came back normal, a state health inspector later found. Some of the guests who came from out-of-state may have also provided documentation that they had tested negative for COVID-19.

Then, about a week after the wedding, guests started to feel sick, Shah said this week. But of the 87 people who had tested positive as of Thursday in connection with the outbreak, just 59 were showing symptoms.

But while the outbreak may have started with a celebration, it has now reached more vulnerable populations.

State investigators have found that an employee of the York County Jail attended the Katahdin-area wedding and was one of the first people to test positive in the jail’s outbreak, which has spread to at least 54 workers and inmates. Until now, Maine had avoided large outbreaks in correctional facilities, where some of the nation’s largest coronavirus outbreaks have happened.

Investigators have also determined that a wedding guest passed the virus to a parent, who passed it to another child who is an employee of Maplecrest Rehabilitation and Living Center in Madison. There are now five cases among residents and four among the center’s staff.

The outbreak has also driven home the importance of measures that public health experts have long recommended for preventing the spread of COVID-19 — including wearing face masks, avoiding large gatherings and staying at least 6 feet away from others — but that apparently were ignored when the guests went to the Big Moose Inn for the reception, according to the health inspector who visited the inn on Aug. 18.

The wedding stood out in a year when many couples have chosen to postpone or dramatically scale back wedding plans — or even drop elaborate plans in favor of eloping.

On Thursday, Maine Health and Human Services Commissioner Jeanne Lambrew acknowledged the special nature of weddings where people converge on a single place from all over to celebrate a couple. But for anyone who is still planning a wedding in the coming days and weeks, she said that there are important reasons for the state’s rules limiting large gatherings.

“As we’ve seen in the last few weeks, there are deadly consequences associated with uncontrolled gatherings,” she said.