Schools in at least 11 states have closed as the worst flu epidemic in nearly a decade intensifies.
The dominant strain of flu this season, H3N2, known for being particularly virulent, has resulted in the deaths of at least 37 children and is expected to cause more as the epidemic persists several more weeks, the Centers for Disease Control and Prevention projected on Friday.
Seven children died this week, authorities said. Hospitalizations, a predictor of the death rate, rose to 41.9 people per 100,000, up from 36.9 the week before.
An estimated total number of deaths due to the flu won’t be available until next season, according to the CDC. Outpatient hospital visits by people with the flu have been skyrocketing for several weeks, and as of mid-January had surpassed every season except 2009-10, when a new strain of flu caused a global pandemic.
Some states are tracking flu-related deaths. Texas is reporting 2,355 flu-related deaths from October through December. The state expects that number to rise dramatically, but said it was too early to tell if it will exceed last season’s flu-related death toll of about 9,500.
The flu is particularly hard to fight this year because the H3N2 strain tends to strike the elderly and children hard. People over age 65, and between the ages of 50 and 64, are being hospitalized at higher rates, the CDC said.
The vaccine works especially poorly this year. Preliminary data suggest the shots are likely about 30% effective against H3N2 and closer to 40% against all viruses that they include, said Daniel Jernigan, director of the CDC’s Influenza Division.
Schools closed anywhere from a day to a week due to widespread absenteeism as administrators try to stop the spread of the virus and disinfect buildings. Several school administrators said they have never seen closures of this scale.
Gulf District Schools in Port St. Joe, Fla., closed its four campuses Friday after about 20% of its 1,900 students missed school on three consecutive days this week due to flulike symptoms.
“We have taken the steps necessary to act in the best interest of children,” said Jim Norton, superintendent of Gulf District Schools. About 25% of his staff also was out sick or taking care of sick children. “We’re going to do a deep cleaning of the schools.”
States with schools that have closed include Texas, Illinois, Oklahoma, Idaho, North Carolina, Tennessee, Florida, Alabama, Kentucky, Michigan and Missouri.
The Melissa Independent School District in Melissa, Texas, plans to stay closed through Monday to disinfect schools. Duncan Middle School in Duncan, Okla., was closed on Friday. The Illinois Mathematics and Science Academy in Aurora, Ill., closed this past Monday for a week due to high levels of influenza cases.
Gunter Independent School District in Gunter, Texas, reopened Wednesday after closing for a week after about 27% of its students, or 253, missed school. A vast majority of students had flu or flu-like symptoms, but some stayed away to avoid getting sick or had other illnesses, said Jill Siler, the district’s superintendent.
It was a tough decision to close without notice, Dr. Siler said. “We closed to stop the cycle,” she added. “We’re talking about almost a third of our population.” The time off also allowed a professional company to come in and clean all schools. “Every single piece in every single classroom was disinfected.”
One big factor in the intense transmission occurring this month may be the return of children to school after the holidays, Dr. Jernigan said. Viruses spread easily among schoolchildren, who spend their days in close quarters and then carry the viruses home.
Flu patients are most contagious during the early phases of their infection. “In particular when they have a runny nose and bad cough,” said Paul Sax, an infectious disease specialist at Brigham and Women’s Hospital in Boston. “That’s a very important time for people to stay out of work and school.”
People can also spread the virus for a period afterward. “When you start to make a turnaround and you start to feel better, give yourself another five to seven days,” he said.
Around 60% of children under the age of 18 are vaccinated, Dr. Jernigan said. Among children aged 13 to 17, the rate is 46.8%, and among 5 to 12 year-olds, the rate is 61.8%.
“The younger you are, the better your vaccine coverage,” he said.
The CDC said on Friday outpatient visits for flu symptoms increased to 6.6% of all outpatient visits, from 6.3% the previous week. Hospitalization rates are now similar to those of the 2014-15 flu season, when up to 56,000 people died from flu-related illnesses, the CDC estimates. H3N2 also predominated in that season, Dr. Jernigan said.