WASHINGTON – An unvaccinated teacher at an elementary school in California spread the coronavirus to at least 26 other people, including 12 students in their classroom, said a new study by the Centres for Disease Control and Prevention (CDC) yesterday.
The health agency said the case highlights the importance of vaccinating school staff to protect young children who are not yet eligible for vaccination, as schools reopen amid a new nationwide surge driven by the ultra-contagious Delta variant.
CDC said the incident took place in Marin County, a suburb of San Francisco.
The teacher, who reported attending social functions from May 13 to 16, became symptomatic on May 19 but did not take a Covid-19 test until May 21, initially believing the symptoms were due to allergies.
“On occasion during this time, the teacher read aloud unmasked to the class despite school requirements to mask while indoors,” said the study.
In the days that followed, among the teacher’s 24 students, all ineligible for vaccination because they are under 12, 22 received tests and 12 were found positive.
Eight out of 10 students in the two front rows tested positive, an attack rate of 80%, as well as four out of 14 in the three back rows.
The school required students to mask, each student’s desk was set 1.8m from the next, windows were open on both sides of the classroom, and a high-efficiency particulate air filter was placed in front of the whiteboard.
Six students in a separate grade also tested positive.
It is not clear how the virus spread between the two classes, with researchers presuming an interaction occurred at school.
However, genetic sequencing of available samples confirmed they were all part of the same outbreak, and identified Delta as responsible.
Eight additional cases were identified among the parents and siblings of children in the two grades. Among the four parents infected, three were fully vaccinated.
Twenty-two of the total 27 infected people (81%) experienced symptoms, the most frequently reported being fever, followed by cough, headache and sore throat.
No one involved in the outbreak was hospitalised.
CDC said the outbreak is likely underestimated because all testing was voluntary.
“The outbreak’s attack rate highlights the Delta variant’s increased transmissibility and potential for rapid spread, especially in unvaccinated populations such as schoolchildren too young for vaccination,” said the report’s authors.
What works
In addition to vaccinating school staff, the authors stressed the need for multipronged mitigation strategies, including using masks, ensuring distancing and ventilation, and staying home when sick.
A second CDC study also released yesterday was held up by the agency’s director Rochelle Walensky as an example of what happens when best practices are followed.
It showed that during the winter pandemic peak, case rates among children and adolescents in Los Angeles county schools stood at nearly 3.5 times lower than rates in the surrounding community.
“We know what works. Now, let us unify together to follow these steps to ensure fundamentally that our children and our future are safe,” Walensky told a press briefing. – AFP, August 28, 2021
