PORTLAND – Spring may be in the air but so is influenza, which appears to be reaching its peak across the region.

A late influenza onslaught is hitting Maine and New Hampshire with a growing number of hospital admissions and sporadic outbreaks at schools and nursing homes across the region, public health officials said Thursday.

In Maine, two hospitals reported that 8.4 percent of emergency room admissions were related to respiratory illness in the latest weekly reporting period. One school reported that 15 percent of students and teachers were absent.

Overall, it has been a relatively mild influenza season, and the flu should be on the way out by this time of year in New England.

“We know that the most predictable thing about influenza is that it’s unpredictable. So this late peak is evidence of that,” said Dr. Dora Anne Mills, director of the Maine Centers for Disease Control and Prevention in Augusta.

The number of laboratory-confirmed cases of influenza recorded weekly at Eastern Maine Medical Center in Bangor started to rise on March 5, according to Dr. Kirk Doing, director of the hospital’s infectious disease lab.

“We now have 20 to 25 laboratory-confirmed cases weekly,” Doing said Thursday. Some good news, however, is that the viruses being identified are very closely matched to the strain that this season’s flu shots were tailored to build immunity against.

Until recently, Maine Medical Center was admitting one patient a week with laboratory-confirmed influenza. Starting in the middle of last week, the number has grown to at least one flu admission each day.

“That’s the ones we know about. There are others who come in who don’t get tested,” said Gwen Rogers, a nurse epidemiologist and manager of infection control at the state’s largest hospital.

Also troubling, Mills said, is that the number of deaths in Maine’s biggest cities has increased as well. According to the latest report, 7.3 percent of deaths were due to influenza or pneumonia.

New Hampshire also is seeing an upswing in influenza. From March 5 to 11, the New Hampshire Public Laboratories received 36 flu specimens, 32 of which were positive, according to the state’s latest influenza report.

“This is a very peculiar year for flu,” said Greg Moore, spokesman for the New Hampshire Department of Health and Human Services.

The winter flu season typically starts in California before moving eastward across the nation. West Coast states are now seeing less flu activity.

All told, 37 states – including all six in New England – reported widespread or regional influenza activity in the week ending March 18, according to the Centers for Disease Control and Prevention in Atlanta. Thirteen states reported only local or sporadic activity.

The flu season is expected to draw to a close shortly. It typically ends as warmer weather arrives at the end of March and early April.

For now, public health officials are urging people not to forget the three rules for avoiding influenza and other bugs: Wash hands frequently, cover coughs and sneezes, and stay home when ill.

BDN writer April Forristall contributed to this report.