More certain than snow, more contagious than Christmas cheer, those winter viruses that cause influenza, flulike illnesses and the intestinal yuks have Marylanders in their grip.
In Baltimore, some doctors and hospitals said their offices and clinics have been jammed the last two weeks with adults and children seeking relief from dry, hacking coughs, congestion, fever, chills and aches -- the classic flu symptoms.
Many patients have a mixture of symptoms that include vomiting and diarrhea.
"Yes, we're seeing lots of flu," said Dr. Kevin Ferentz, the director of student and employee health at University of Maryland at Baltimore, who also sees other patients in the hospital's clinics. "We're seeing it, really, in the whole age group."
State health officials have cultured the influenza A virus in 14 cases, said Dr. Betsy Thompson, medical epidemiologist, proof that the flu virus is making its rounds in Maryland.
But doctors say they rarely culture patients and simply treat the symptoms, because it takes a week to get results of the culture back from a laboratory and by then the illness is likely to be over.
Doctors predict the flu and flulike illnesses will continue to attack Marylanders for another month or two.
More than 80 schools, elementary through high schools, have reported more than 10 percent absenteeism to the Maryland Department of Health and Mental Hygiene since flu season began in November, said Dr. Betsy Thompson, medical epidemiologist.
"The day after Christmas, I saw 35 kids" with flulike illness, said Dr. Oscar Taube, medical director of the pediatric outpatient department at Sinai Hospital. "We saw over 100 a week the last two weeks, mainly infants, toddlers and young school-age kids."
The illness lasts four to seven days and often makes a first appearance, seems to be over, but then comes back with "an encore," he said.
Patients often feel "like somebody snuck into their bed and beat them up with a baseball bat," Dr. Taube said.
Parents should keep children home, give them acetaminophen -- not aspirin -- for fever and aches, and ask them to drink a lot of liquids, he said. A vaporizer or humidifier by the crib or bed can help alleviate congestion.
In Carroll County, flu began hitting schools just before winter break, said Georgia Cox, a secretary for the school administration. On one day last month, eight schools reported record absences, she said. Manchester and Charles Carroll elementary schools were struck hardest, with nearly a quarter of their student body and several teachers out.
"It was chaos in the classroom," said Robert C. Bruce, principal of Charles Carroll Elementary School near Westminster.
Some Baltimore County schools have experienced high absenteeism from flulike illness, but flu is no longer making much impact on the county's 147 schools, a spokeswoman for the county Health Department said yesterday.
Flu or similar illnesses are continuing to strike adults in Maryland, often lasting for about a week.
Since mid-December, more than 20 nursing homes have had outbreaks of flu or flulike illness, and three nursing home residents who had flu have died, although the cause of their deaths has not been confirmed, the state health department reported.
Other nursing homes report cases of the diarrheal illness of the sort that briefly felled President Bush yesterday at a dinner in Japan.
Health officials say it is not too late to get flu shots. People over age 65 and anyone who has chronic respiratory, pulmonary or heart problems or diabetes is at high risk for getting serious complications from flu and is advised to get flu shots.