COVID testing program helping Baltimore City school system track and contain infections

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Baltimore City’s school system is now testing more than 15,000 people each week for COVID-19 — frequently before students and staff show any symptoms — in an effort to prevent the spread of infections within schools.

The school system is now one of the city’s largest COVID testing sources, and has become a model for districts around the country.


The schools employ saliva-based molecular testing for high school students and staff, but use pooled tests for those in kindergarten through eighth grade.

The testing regimen does have shortcomings. Some students and staff who were not infected have been quarantined for two weeks, follow-up testing has been slow and the number of positive tests has concerned teachers union leaders. But school officials and public health experts say the city school system’s testing has largely been a success.


“Baltimore City has been a nationwide leader in testing. We pioneered these strategies,” said Cleo L. Hirsch, director of priority initiatives for the city schools. “It has been an effort to refine and adapt as we go.”

The testing has turned up cases at nearly every school, usually fewer than 10 per school over the course of the last seven weeks of testing. Some 411 COVID-19 cases have been identified since the beginning of the school year. The school system’s testing positivity rate is less than 1%, well below the city’s 2.7% positivity rate, according to state data.

The number of cases that are being discovered is alarming to Zach Taylor, one of the Baltimore Teachers Union’s leaders, but he said the union has been supportive of the district’s move to do the routine testing to make schools safer.

With more people without symptoms now being identified through the city school testing regime, the spread of the virus might be slowed in the city as a whole, said Caitlin Rivers, an infectious disease epidemiologist at the Johns Hopkins Center for Health Security. While she said she is not aware of studies that have looked at the real-world evidence of school testing on slowing transmission, she believes it would have some effect.

“Public schools are deeply connected to communities, and so using them as a touch point to identify infections and outbreaks makes a lot of sense,” she said.

While the individual tests used in high schools are clear-cut, problems have arisen with the pool testing in other grades, Taylor said.

For pool tests, about a dozen people swab the inside of their noses and put the swab in one container. If one of the pools has a positive test, then those 12 individuals get further tests.

Taylor said that one of the issues that has come up is a failure by the school system to get second tests quickly for those in positive pools. While staff and teachers can often go to a pharmacy or other location, families don’t always have the ability to test their children immediately and can wait days to get the test and a result.


Hirsch said the school system has added two more mobile labs, for a total of three, to cut the time students have to wait for a test. The tests usually can be done in two days, she said.

Meanwhile, all those in a positive pool are asked to quarantine for two weeks.

“The quarantine is a challenge. It is a challenge for families and hard on the kid who wants to be back in school,” she said, but she added that she believes schools are safer places because of it.

Hirsch said the largest share of the work has been done by school principals who have had to juggle the testing along with many other difficult issues related to reopening.

Since the city schools started their testing in March, other large school systems, including Montgomery County, have begun to as well.

Across the nation, more school systems have started regular testing of staff and students. Newark and Maine recently began offering pool testing through Ginkgo Bioworks Inc., the company the city school system is using.


Christina Agapakis, a biologist and creative director at Ginkgo Bioworks, said the company is now testing at more than 1,000 schools.

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“I think Baltimore has been a real leader here,” she said.

Most of the $15 million for city school testing this year will come out of the school system’s operating budget, but the Rockefeller Foundation also is providing $1.49 million to cover some of the cost of the saliva tests being given to high schoolers and staff.

Andrew Sweet, who heads Rockefeller’s COVID-19 response team, said a coalition of universities in the region came together to ensure that there was enough testing capacity to help local school systems.

“One of the priorities of the foundation is to make sure students can go back to school,” Sweet said.

Baltimore was chosen, he said, in part because of schools chief Sonja Santelises, who is viewed as a national leader among other urban school superintendents. If Baltimore was able to begin testing, he said, then other school districts would follow.


“It was exciting to us because of the outsized influence we hear Sonja Santelises has across the country,” Sweet said.

The grant will not continue past this school year, he said, but Maryland is expected to get about $180 million for testing from the federal government as part of the recently approved federal COVID relief bill.