BOSTON -- Public health experts in Massachusetts expect a jump in the number of H1N1 flu cases, as tens of thousands of students return to schools statewide.

“It usually takes a few days to a week for the germs to incubate,” said Mimi Stamer, the new president of the Massachusetts School Nurse Organization. “So it isn’t unusual that week two of school, some children may have some symptoms of illness.”

“We can expect a much larger number of cases,” said Julio Frenk, dean of Harvard’s School of Public Health, who has been monitoring the H1N1 flu in the southern hemisphere, where winter is now ending.

“The good news is that the virus has not mutated into a more severe form,” he said.

According to statistics provided by the Massachusetts department of public health, 62 percent of H1N1 cases confirmed statewide since April have impacted children age 18 and under. While the vast majority of those cases have not been serious, the large percentage has many parents and educators taking extra precautions.

Many experts NewsCenter 5 consulted said it is a good idea for children to be armed with common sense supplies when they return to class.

“It's important that children understand that carrying around hand sanitizer is socially acceptable. Having Kleenex on you is wise,” said Dr. Les Selbovitz, chief medical officer at Newton Wellesley Hospital.

“It’s probably a good idea,” agreed Stamer. “A parent could stick a little packet inside their child's lunchbox.”

A special government grant to help contain the number of H1N1 cases is paying for extra supplies of hand sanitizer, soap and tissues in schools. Nearly every school in the Commonwealth is installing additional hand sanitizer dispensers.

Teachers may be advised to schedule hand-washing breaks during the school day, and teach children proper cough etiquette.

“We think those steps will help limit the spread of the flu,” said Boston school superintendent Carol Johnson.

When students do display flu symptoms, school nurses will keep them separated from others until they can go home. Sick children may even be asked to wear a mask.

Guidelines from the Centers for Disease Control and Prevention strongly encourage anyone with flu symptoms to stay home from school or work to limit the possibility they might spread of the virus to others.

“If the child does prevent with fever sore throat or cough,” Stamer said. “Then we're encouraging them to stay home for 24 hours off fever reducing medicine and no fever.

Public health officials in Massachusetts said it won’t surprise them if some schools, or some districts have absentee rates as high as 20 percent once the flu season kicks in.

Because the H1N1 vaccine isn’t expected to be ready until October, it will likely be November before there is widespread immunity. It is anticipated that most people will require two doses of the new vaccine, given three weeks apart. Immunity from the H1N1 virus would not be likely until two weeks after the second dose is administered.