While there is no aggregate rate for migrants, test results from several significant corridors for illegal border crossings suggest it is well below levels that have triggered concerns among U.S. officials. According to the state Department of Social Services, 54 of 2,877 migrants tested positive the first two weeks of March in California. That's a rate of just 1.9%, down from a peak of 28.2% on January 8. In Pima County, Arizona, which includes Tucson, the seven-day positivity rate among migrants didn't exceed 1.3% in early March and dropped to 0.9% on March 10.