106 Screened at School Test Positive for TB : Medicine: Health official concedes La Quinta results were unexpected. Origin of the new infections is being investigated.

WESTMINSTER —  A second round of tuberculosis screening at La Quinta High School shows that as many as 106 additional students and staff are infected with the bacteria that could cause the disease in the future, authorities said.

But Orange County Health Officer Hugh Stallworth said that no more students were found with active TB.

Stallworth conceded that the large number of people--97 students and nine staff members--whose skin tests turned up positive last week was unexpected.

Those who tested positive are carrying the bacteria but are not ill or contagious. Medical experts say they have a 10% chance of contracting the disease over their lifetime but that probability can be greatly reduced by taking preventive medication.

The test results are the latest development in the county’s battle against tuberculosis at La Quinta, which has had the nation’s largest outbreak ever of drug-resistant tuberculosis at a high school. Since 1991, 17 students have been diagnosed with active TB--12 of those with the more serious drug-resistant strain.

Stallworth said all of the students who tested positive for the bacteria last week will be interviewed this week to determine how many people contracted the bacteria from a senior, Debi French, who relapsed with a highly drug-resistant strain of the disease late last year. Part of French’s lung was removed last month to halt the disease after first-line medications failed.

French was contagious sometime between December and February, when she was diagnosed and removed from school, county officials have said. The county had ordered last week’s schoolwide screening after a preliminary screening of those close to French revealed that the skin tests of 18 students and two staff members were positive.

Stallworth said it is important to determine the origin of the new infections to give each person the appropriate preventive medications. He said of the 106 who tested positive, about a third of the results were in an “intermediate range,” which means they may not actually have been exposed to the disease and the positive finding may be incorrect. The only way to tell for sure, he said, is to investigate whether they have been in contact with TB patients.

Stallworth said the county will receive help from the state Department of Health Services and the Centers for Disease Control and Prevention in conducting the follow-up interviews. Last fall, after the 17 active cases of tuberculosis were identified at La Quinta, another schoolwide testing of the 1,300-member student body found 175 students who skin-tested positive. Most of these will have completed a six-month program of preventive medication by the end of the week, when school closes for the summer.