In this Sept. 8, 2021, file photo, a couple wears face coverings in Portland. Credit: Robert F. Bukaty / AP

COVID-19 case levels remain high in Maine even as they decline nationally, suggesting continued public health challenges remain as winter approaches.

Maine is one of just six states where the infection rate remains higher than two weeks ago, alongside South Dakota, Colorado, Utah, New Mexico and Idaho, according to a New York Times analysis. Although 13 states saw worse virus situations over the past week, it highlights how difficult it has been for Maine to turn the corner after the late-summer delta variant surge.

Virus cases in Maine appeared to peak in late September and dropped notably in the first two weeks of October, but have been back on the rise again in the past two weeks, Maine Center for Disease Control and Prevention data show.

The higher case levels have challenged Maine hospitals, which have seen near-record COVID-19 patient numbers in recent days. MaineHealth, the state’s largest hospital system is currently diverting patients from Maine Medical Center amid staff shortages and high caseloads.

Nationwide, COVID-19 cases have been declining since mid-September. Hospitalizations also continue to drop, with the seven-day average 19 percent lower, compared with two weeks ago, according to the Times analysis.

The decline in infections was initially driven by drops in southern states that were first to see the widespread effects of the delta strain earlier this year. The more contagious variant took off in New England later, although other states in the region, including Massachusetts, Rhode Island and Connecticut, have begun to see cases drop in recent weeks after surging in September.

The drop has been less significant in northern New England states, but Vermont and New Hampshire have seen their infection rates decline slightly over the past two weeks, while Maine’s has fluctuated somewhat but ticked upward on net.

Within Maine, recent virus cases continue to be correlated with local vaccination rates. Maine’s least-vaccinated county, Somerset, also has the highest current seven-day case rate, more than three times higher than that of Cumberland County, which currently has the lowest case rate and highest vaccination rate.

That fits with a trend of parts of Maine with lower vaccination rates seeing more cases. ZIP-code level data in September showed cases were 40 percent lower in towns with vaccination rates above 90 percent, compared with those with vaccination rates below 70 percent. School outbreaks are also most common in counties with low vaccination rates and high overall case rates.