HUNTINGTON, Ind. (AP) _ Public health officials tried Monday to determine the extent and cause of a flu-like respiratory disease that temporarily closed a junior high school.

Students, parents and staff of all Huntington area schools were being surveyed to determine if the outbreak was isolated at the closed Riverview Junior High School.

''We're predominantly focusing on the question of 'Is this localized to the junior high school?' today,'' said Dr. Michael Linnan, an epidemiologist for the U.S. Centers for Disease Control in Atlanta.

Linnan said there was no preliminary indication of a larger outbreak of the ailment, believed to be histoplasmosis.

On March 19 when 131 of Riverview's 540 students stayed home due to illness. The absentee rate later declined to about 60, but was still above the usual average of 16 to 27 absences per day, officials reported.

Superintendent Roger Schnepf of Huntington County Community Schools said the school board voted unanimously to close the school this week while the investigation continues.

Histoplasmosis, an infection that usually attacks the lungs, is caused when certain yeast spores are inhaled, settle into the lungs and multiply. The spores, which travel through the wind, most often originate from bird, animal or human waste sites.Symptoms include fever, chest pain, coughing and fatigue.

One case of the non-contagious disease has been confirmed in a school staff member, and four other cases, including two students, appear ''very likely,'' said Dr. Robert H. Hamm, medical epidemiologist for the Indiana State Board of Health.

''Because it now appears there in fact is a real outbreak of histoplasmosis in this one school, we're starting to look for possible sources,'' said Hamm.

Officials said the source may or may not be on the school grounds. Hamm said the spores may have come from a recently cleared wooded area, and officials will try to locate such a site this week.

About 80 parents attended an emergency meeting of the school board Saturday to express concern for possible health hazards around the school, according to Schnepf.

Meanwhile, Hamm assured victims that the disease is rarely life- threatening.

''The vast majority are going to have an illness that lasts about two weeks, and they'll get over it without any treatment,'' Hamm said. The most severe cases may require hospitalization and anti-fungal treatment.