July 15, 2020 -- An American school teacher who traveled to Europe in February and then taught for several days before testing positive for COVID-19 may have passed the coronavirus to students, according to a new study by the CDC. The results were published online as an early release article from the journal of Emerging Infectious Diseases, and could be updated before the official release in September.
“Classroom contact may result in virus transmission,” the authors wrote.
The study could indicate how coronavirus transmission might happen in schools, but it has several limitations, the research team wrote. They weren’t able to record how much contact each student had with the teacher, for instance, which could give insight into whether social distancing could work in the classroom. They also conducted the blood tests about 14 days after exposure, which may have been too soon to detect antibodies.
Finally, the researchers were only able to test and survey the 21 students out of 192 students rather than all students who were in the classroom, which could change the picture of how many students contracted COVID-19, had antibodies or experienced symptoms.
Additionally, this situation occurred in a symptomatic teacher, with no covid-19 precautions such as masks and social distancing.
The teacher experienced flu-like symptoms such as a headache, sore throat, muscle pain and fatigue while she was traveling in Europe, where the coronavirus had already begun to spread from person to person. After arriving home, she taught between Feb. 24-27 with the same symptoms and a mild cough. She was tested for COVID-19 on March 1, and the result was positive.
The students in her classroom were instructed to quarantine at home until March 12, and after the isolation period, 21 students took blood tests. Two students had antibodies that suggested a past infection with SARS-CoV-2, the virus that causes COVID-19, and nine others reported symptoms.
During the few days in the classroom at the end of February, the teacher had 16 classes in the same room, and each class had 30 or fewer students. Among the classes, 10 were interactive, discussion-based classes where the teacher walked around the room and talked with students. During the other six classes, the teacher sat in one location and didn’t have close interactions with students.
The research team contacted 120 students who were in the interactive classes and 72 who were in the non-interactive classes who may have been exposed. Their only known exposure was through classroom contact with the teacher. The researchers invited all students to take blood tests, and 21 accepted.
Among the 21, five were in the interactive classes, and 16 were in the non-interactive classes. Two of the five in the interactive classes had antibodies that suggested a previous infection. The two students weren’t in the classroom at the same time and sat in different locations in the room.
The first student, who had a higher antibody result, spent 135 minutes in the interactive classes. On Feb. 26, the student had a cough, runny nose and muscle pain that lasted for nine days. The second student, who had a lower antibody result, spent 90 minutes in the interactive classroom and reported no symptoms.
Among the three students in the interactive classes without a positive test, two reported symptoms such as a fever, headache and runny nose. In the non-interactive classes, seven students reported symptoms such as a sore throat, headache, runny nose and muscle pain but had no positive results on their blood test.
“Widespread school closures have mostly eliminated the risk for classroom transmission of SARS-CoV-2,” the authors wrote. “However, these results suggest that classroom interaction between an infected teacher and students might results in virus transmission.”