One out of every three students at Arlington County's Williamsburg Intermediate School yesterday took the day off, but they probably would have preferred to spend a normal day in class.

Instead, they were at home suffering from a fever, headache, hacking cough, scratchy throat, aching muscles and, now that you mention it, feeling rotten all over. Like thousands of other people in the Washington area, they had the flu.

Influenza has ripped like a brush fire through area schools and offices, leaving empty desks and teacher shortages.

But health officials said yesterday they have little evidence so far to suggest that this year's flu season is more widespread or dangerous than usual.

"This appears to be the 1986 model" of the flu season, which usually strikes the area this time of year, said Fred Payne, a Fairfax County health official.

The test of the severity of influenza this year, Payne added, will come in the next several days, as officials monitor the number of cases and the ages of persons most affected.

Because most people develop an immunity to types of flu they have already had, if a large number of elderly persons get the flu, it usually means it's a brand new virus.

Area schools -- where outbreaks of flu are easiest to detect because of high numbers of absentees -- are already reeling from the flu.

At Williamsburg, about 30 percent of the school's seventh and eighth graders were absent yesterday, and about 35 percent stayed home the day before.

In Montgomery County, a spokeswoman said that a survey showed that 17 schools had more than 15 percent of students sick. In Fairfax County, absentee rates are double their usual number.

D.C. schools have had better luck avoiding the virus. Yesterday they reported a normal rate of about 10 percent not present, reflecting no rise because of the flu, said spokesman Maurice Sykes.

It wasn't just children suffering from the flu yesterday.

Enrico Davoli, a McLean pediatrician whose waiting rooms have been filled with flu patients this week, said in many cases entire families have come down with the bug.

"I have a mild case of it myself. I don't know what I'm doing working here," Davoli said, signing off with a sneeze.

Most of this year's flu cases appear to be of the "type B" virus, a strain that has been seen less often in recent years, said Dr. Feng-Ying C. Lin, a Maryland health official.

Type B viruses can be more worrisome than their "type A" cousins, Lin said, because they are not treatable with antiflu drugs.

Also, researchers suspect a link between taking aspirin when suffering from type B influenza and contracting Reye's syndrome, a dangerous swelling of the brain that mainly afflicts children.

Payne advised people suffering from flu to avoid aspirin except at the instruction of a doctor.

Also noteworthy about this year's flu has been the remarkable speed with which it strikes, Payne said. Rather than building slowly, victims find themselves suffering temperatures as high as 104 degrees in very little time.

The fever usually lasts only a few days at most, Payne said, but most people won't feel completely up to par for several days.

For those unlucky enough to get hit with the flu, Payne acknowledged that there is little to be done but feel lousy. "All the treatment is supportive: fluids, rest, chicken soup. All the things we've always done."