Doug McBride, a spokesman for the Texas Department of Health, said reports of high absenteeism began to come from schools as early as Thanksgiving this year.
"Typically the heavy part of the flu season in Texas is in January and February, but it's not unusual to have a lot of cases in December," he said. "What seems to be a little different this year is we're getting more cases among the elementary, middle school, junior high students," he said.
There have not been school closings caused by the flu in a number of years in Texas, he said.
"Closing a school is not a recommended method of controlling influenza, but that's not to say it doesn't work in a particular situation," he said. "It is a local decision."
Often schools close because they don't have enough students and teachers to conduct classes, he said.
About a dozen small school districts in northeast Texas have closed for one or two days or taken an early weekend this week due to the flu outbreak.
Texas, Tennessee and Colorado were the only states reporting regional outbreaks of the flu in the most recent report by the Centers for Disease Control. Eighteen states reported sporadic activity and 28 states no activity at all. One state did not report.
The DeLeon School District southwest of Fort Worth was closed Friday.
Superintendent Mary Jane Atkins said the district had 65 students missing out of 155 in its middle school Thursday.
"We thought we'd give the kids a three-day weekend to see if that would make a difference in the numbers," she told The Dallas Morning News.
The outbreak is severe because it includes the Hong Kong type B strain, which has not been seen in the United States in about 10 years, according to health officials, who are advising adults and children that it is not too late to get flu shots.
Dr. Robert Haley, chief of epidemiology at the University of Texas Southwestern Medical Center at Dallas, said closing schools isn't likely to lessen the impact of the outbreak.
"Flu is not a school epidemic; it's a community epidemic," he explained "It's going to continue to spread even if children aren't in class. They can get it from their parents."