AUGUSTA — State health officials are investigating COVID-19 outbreaks among staff at Maine Medical Center in Portland and Waldo County General Hospital as the number of coronavirus cases continues to rise in many communities.

Nine members of Maine Medical Center’s emergency department have tested positive for COVID-19 since last week. The nine employees worked in clinical care. Hospital staff contacted all patients who were potentially exposed while visiting the emergency department and offered testing.

There have been no positive cases so far among patients who had contact with the infected staff members, some of whom were fully vaccinated against the virus.

“In accordance with CDC guidance, (Maine Medical Center) has tested its full ED team and is further expanding testing to evaluate ED support staff,” the hospital said in a statement. “We will continue to test the ED team at regular intervals.”

The Maine Center for Disease Control and Prevention also has opened an investigation into an outbreak involving eight staff at Belfast’s Waldo County General Hospital.

“Following CDC guidelines, the colleagues are in isolation at home,” hospital spokeswoman Jenifer Harris said in a statement. “Everyone considered to be close contacts with those who tested positive has been informed. It is believed that the cases are an indication of community spread in Waldo County, which is considered a high transmission county by the CDC.”

Waldo County, a COVID-19 hotspot in Maine, has an infection rate that his nearly three times higher than the U.S. CDC’s high transmission threshold.

The Maine CDC also was investigating at least seven other outbreaks, which are defined as three or more cases with a common link. Four of the investigations centered on Pratt and Whitney, Camp Caribou, Camp Laurel South and Zion Pentecostal Church. Maine CDC spokesman Robert Long said the agency also is investigating outbreaks at three other locations but did not identify them.

COVID-19 cases have been rising sharply in Maine and across the country in recent weeks due, in large part, to the emergence of the highly transmissible and potentially more dangerous delta variant.

No new case data was available Monday because the Maine CDC only provides updated figures Tuesday through Saturday. But as of Saturday, the average number of new COVID-19 cases in Maine has increased sixfold – to 124 cases per day – in the past month.

The vast majority of those cases as well as hospitalizations have been among unvaccinated individuals. There have been least 712 “breakthrough” infections and 14 deaths among vaccinated individuals in Maine, although state health officials have said breakthrough cases are to be expected because no vaccine is 100 percent effective. The risk of being hospitalized or dying from COVID-19 is 25 times lower for fully vaccinated individuals than for unvaccinated individuals, according to federal estimates.

VACCINATION RATE TICKS UPWARD

At the same time, the Mills administration announced Monday that Maine had surpassed another symbolic milestone, joining five other states that have administered COVID-19 vaccine shots to at least 80 percent of residents age 18 or older. The Maine CDC reported Monday that the number of vaccine shots administered daily rose roughly 12 percent from an average of 1,497 for the week ending July 30 to 1,673 for the week that ended Sunday.

As of Monday, 69.3 percent of residents 12 or older who are eligible for vaccination had received their final doses of either the Moderna, Pfizer or Johnson & Johnson vaccines. That figure rises to 80.2 percent when zeroing in on those age 18 or older who have received at least one shot, the Mills administration said on Monday.

Maine currently ranks third in the nation, after Vermont and Massachusetts, in terms of the percentage of the entire population that is considered fully vaccinated, according to tracking by Bloomberg.

“I applaud Maine people for their willingness to roll up their sleeves and get their shot,” Gov. Janet Mills said in a statement. “We know that vaccinations are the best tool to protect the health of Maine people, and with the more contagious and deadly delta variant spreading across Maine and the nation, it is crucial that we continue to make progress and fight back against this pandemic. If you haven’t had your shot yet, I encourage you to talk to your doctor about how getting vaccinated can protect your health and potentially save your life.”

At the same time, the latest data from the Maine CDC shows how quickly the delta variant has become the dominant strain in Maine.

In July, the delta variant accounted for 86 percent of the 115 positive test results that were analyzed with genomic sequencing to determine the strain of the coronavirus. By comparison, the delta variant was detected in just 3.3 percent of the positive tests that were sequenced in Maine during June.

DELTA VARIANT FUELING SURGE

The delta variant accounted for roughly 93 percent of the sequenced cases nationwide as of the end of July, according to estimates last week from the U.S. CDC.

Masking is once again recommended for both vaccinated and unvaccinated individuals in indoor, public settings in seven of Maine’s 16 counties because case rates exceeded 50 people for every 100,000 residents in the previous week.

Cumberland, York, Knox, Penobscot and Aroostook counties were all experiencing “substantial” levels of community transmission as of late last week, based on the U.S. CDC’s system of tracking cases nationwide. Waldo and Piscataquis counties were experiencing “high” transmission rates.

Cases have been growing the fastest, by far, in Waldo County when compared to the local population base. As of Friday, the most recent figures available, Waldo County was seeing 290 new cases of COVID-19 for every 100,000 residents, which is nearly triple the rate in Piscataquis County, quadruple the rate for Cumberland County and five times the rates seen during the same period in York County.

Long, the Maine CDC spokesman, said agency staff continue to investigate the reasons behind the surge in Waldo, a largely rural county that has consistently had among the lowest infection rates in the state throughout the pandemic.

“Case investigations continue to indicate that the increase in Waldo County cases results from community transmission, primarily among people who are not fully vaccinated,” Long wrote in an email.