A woman wears a mask to protect against the spread of the coronavirus while walking by a hardware store, Wednesday, Sept. 9, 2020, in Sanford. Credit: Robert F. Bukaty / AP

Maine health officials have been sounding the alarm about the spread of COVID-19 in York County in recent weeks, saying the state could lose its grip on the disease if cases continue to grow in Maine’s southernmost county.

State data over the past month tell the story of the virus’ accelerating spread in York County, which has been responsible for about 40 percent of the state’s new virus cases since mid-August, even though it’s home to only 15 percent of the state’s population. It has seen its number of active cases more than double in that time, from 61 on Aug. 15 to 152 on Thursday.

York County roughly followed state trends for new daily cases and active COVID-19 cases among its residents for most of the spring and summer. But the county’s fortunes changed in mid-August, following an Aug. 7 wedding in the Katahdin region whose ripple effects have largely been felt more than 200 miles to the south.

The York County Jail in Alfred, with more than 80 linked cases, is now the site of Maine’s largest outbreak to date in a correctional facility, after a jail employee attended the wedding and brought the virus back.

And there are a number of other smaller outbreaks in the county, many revolving around Sanford, where the church of the pastor who officiated the Aug. 7 wedding, a handful of private social clubs and a manufacturing plant are now official outbreak sites.

This week provided fresh evidence of how the county’s surging virus activity is leading to new outbreaks, after the state reported 18 virus cases at the Portsmouth Naval Shipyard in Kittery, likely linked to a group of people who commute together to the shipyard from Sanford.

The state’s regularly updated data on new and active cases, as well as case data by ZIP code that the CDC updates weekly, offer signs of how the virus has been spreading in Maine’s southernmost county.

York County towns have been moving up in the ranks in state infection rate data.

Four weeks ago, on Aug. 23, Sanford ranked 57th in the state in the number of reported cases for every 1,000 residents. Four weeks later, on Sept. 13, Sanford ranked 25th. Neighboring Alfred, home to the York County Jail, rose from 55th to seventh.

Springvale, a part of Sanford, moved up from 67th in the state on Aug. 23 to 28th on Sept. 13. Acton moved from 22nd to 11th and Limington rose from 47th to 33rd. Those are only some of the York County communities that saw their infection rates grow.

Another town that has seen a marked rise in its infection rate in that time is the Somerset County town of Madison, home to Maplecrest Rehabilitation and Living Center, where 39 residents and employees became infected with the coronavirus and six residents have died.

As in York County, Maplecrest’s outbreak is a result of the Aug. 7 wedding, after an employee became infected from a parent who picked up the infection from another child who attended the wedding.

Madison’s infection rate on Aug. 23 was 59th highest in the state. Four weeks later, it was 10th.

York County dominates the top 10 Maine towns for the rate at which their infection rates have grown in the past four weeks.

Communities in the state’s southernmost county occupy eight of the top 10 slots for the growth in infection rates between Aug. 23 and Sept. 13. Alfred tops the list, with a 289 percent increase in the number of cases per 1,000 residents in that time. One of the only two communities not in York County to make the top 10 list is Madison, which saw its infection rate rise 260 percent in that four-week period, providing further evidence of the wedding’s impact.

York County has essentially traded places with Cumberland County in the rate of daily new cases.

For much of the spring and summer, Maine’s virus cases were most concentrated in Cumberland County, where the daily rate of new cases was consistently double the statewide rate from April to early July, while York County’s rate roughly tracked the state’s.

York County overtook Cumberland County in mid-August, and its daily rate of new cases has exceeded Cumberland’s and the rest of the state’s ever since, when measured as a rolling, seven-day average of new virus cases per 10,000 residents.

Cumberland County, meanwhile, has roughly tracked the state rate since about Aug. 20.

York County has also overtaken Cumberland in the number of active coronavirus infections for every 10,000 residents.

While the change in fortunes in York County is distinct, it’s not the only place in the state with worrisome trends.

While York County had the highest positivity rate — the percent of coronavirus tests coming back positive — in Maine over the past two weeks (2 percent), rural Somerset (1.9 percent) and Oxford (1.6 percent) counties are close behind. The statewide rate was 0.5 percent.

Those three counties also have had the highest rates of new cases over the past two weeks. Oxford County, which saw an outbreak this week at the ND Paper mill in Rumford, was responsible for about a third of the 46 new cases reported Friday.

“Case counts are increasing in counties that previously had few cases,” Maine CDC Director Nirav Shah said Tuesday. “We’ve opened several outbreak investigations just in the past few days in counties across the state where there were previously very few outbreaks, providing further evidence that the virus is here. And by here, I mean everywhere.”