With growing global concern over the coronavirus, Island health officials are bracing for another historic year for a more familiar virus: the flu.

This week, the Massachusetts Department of Public Health announced that influenza severity in the state has increased from moderate to high, affecting schools and businesses statewide and on the Island. More than 90 students were absent from the West Tisbury School on a single day last week, an unknown number linked to the flu, though attendance has since returned to more normal levels.

Since October, the Martha’s Vineyard Hospital has confirmed 118 cases of the flu, a number that is likely to climb in the coming weeks as flu season reaches its peak. The majority of the flu tests showed type B flu, which is less contagious but equally as debilitating as its type A counterpart. Flu shots protect against both strains.

Last year, the hospital reported the highest rate of flu-related visits since the 2009 swine flu pandemic, and health officials see a similar trend developing this year.

“The amount of positive flu [cases] is almost exactly identical to last year at this time,” said Claire Seguin, chief clinical and quality officer at the hospital. “It can be kind of unpredictable, but the next weeks bring the main spike in the flu season.”

Last year’s uptick in flu activity prompted the few walk-in clinics on the Island to start vaccinating in October, with the result that the antiviral vaccine for flu has become harder to find.

Vineyard Scripts, Stop & Shop Pharmacy and Conroy’s Apothecary, the only public clinics on the Island that deliver the flu vaccine, have all run out of regular dose vaccines. They are still in stock for high dose vaccines, only recommended for people aged 65 and up.

“We started vaccinating early in the season and a lot of people came in, probably due to what was in the media, that it was going to potentially be a severe and early flu season,” said Tamara Hersh, co-owner of Conroy’s pharmacy in West Tisbury.

Though the Martha’s Vineyard Hospital still has a supply of regular and high-dose vaccines, Island Health agents said they were concerned with the vaccine shortage and are hoping to counter it with a late-season flu immunization clinic — though there is not yet an official plan. “When something gets going, it takes on a bit of momentum,” said Chilmark health agent Marina Lent. “If it’s shaping up that there is a [vaccine] shortage, we’re going to try to rattle the cage and hold a pop-up clinic.”

The national supply chain for the vaccine, produced by private manufacturers to meet a demand that varies each year, has grown fragile in recent years. As demand climbs, so does the likelihood that the manufacturers will have to discard any surplus of the expensive vaccines at the end of the flu season. To cut down on waste, supply is often limited.

This year, as in previous years, the trend has been felt on a local level.

“Once the manufacturers sell out, they’re out,” Ms. Hersh said. “It seemed like there was a production problem around October, and now that supply is exhausted.”

Symptoms of the flu include fever, chills, sore throat, fatigue, coughing, headaches and sometimes vomiting or diarrhea. The flu kills roughly 35,000 people each year and hospitalizes about 200,000 in the United States, according to the Centers for Disease Control and Prevention. It is especially dangerous for adults over 65, children under 5, women who are pregnant and those with a compromised immune system.

Health officials in Massachusetts say they are monitoring a potentially greater threat from the coronavirus that originated in Wuhan, China and has been confirmed in patients in several U.S. states. As of press time, Massachusetts had no reported cases of the coronavirus.

The flu is believed to have been responsible for a spike in absences at the West Tisbury School last Wednesday.

Principal Donna Lowell Bettencourt said 87 K-8 students and five preschool students in Project Headway housed in our school were out in a single day, compared to a typical average of about 30.

The custodial staff gave the school a deep cleaning last week and an outside cleaning company was brought in to thoroughly disinfect all surfaces, door handles, bathrooms, etc., she said.

The Edgartown, Oak Bluffs, Tisbury schools and the regional high school were reporting average or slightly elevated levels of flu activity, according to assistant superintendent Richie Smith.

As a protection against any virus, health officials like Chilmark’s Ms. Lent stress the importance of washing hands and potentially infected surfaces and keeping a distance from those who are sick or contagious.

“We want to get in front of it any, and every, way we can,” she said.