Students at one California school have tested positive for tuberculosis, and other schools across the nation have also recently experienced TB scares.

Forty-five students at one southern California school tested positive for tuberculosis exposure, sparking a fear that’s led administration and health agents on Friday to call for testing off all 1,800 at the building.

The Riverside County Department of Public Health and state authorities have issued a warning for Indio High School students and staffers — but downplayed it a bit, saying “the risk of transmission appears to be moderately low,” in a letter to parents on the school’s website, CNN reported.

Students will be tested on Monday. Those who skip the test won’t be allowed back in the facility until they prove they’re TB-free, CNN reported.

The widespread test was ordered by county health officials after they were surprised by the findings of an initial screening that showed positives were “higher than expected,” a spokesman for the department said, in CNN. That initial screening tested 131 — and 45 came back positive for exposure.

“Someone who is exposed does not necessarily have active tuberculosis, a condition that must be confirmed with more tests,” the spokesman said, in the CNN report. Of those who came back positive for exposure, five were referred for more testing.

In related stories, there has been a confirmed case of tuberculosis at a Henderson, Nevada school and concerns at a Wisconsin district where “… kids in the family with active TB infections attended a Sheboygan high school and middle school”.