The Massachusetts Department of Public Health said the first two influenza deaths occurred in a 6-year-old and a 14-year-old who had significant underlying medical problems. The most recent deaths, however, were children who were healthy before coming down with the flu. Officials said a 15-year-old boy died of bacterial pneumonia related to the flu last Friday and a 12-year-old girl died Sunday, The Boston Globe reported Tuesday.

"This has been a very difficult flu season for the residents of Massachusetts," the state's top epidemiologist Dr. Alfred DeMaria said in a statement. "While flu-related deaths of children are rare, tragically they do occur. These deaths are a reminder that flu is a serious illness that can result in severe consequences for children, particularly those with underlying medical problems."

Flu activity in Massachusetts appears to have peaked the week of Feb. 17, although reports of flu activity are expected to continue into April, state health officials said.