http://ncirs.org.au/sites/default/files/2020-04/NCIRS%20NSW%20Schools%20COVID_Summary_FINAL%20public_26%20April%202020.pdf
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Results
In the 15 schools (10 high school and 5 primary schools) a total of 18 COVID-19 cases (9 students and 9 staff) were identified between 5 March 2020 and 3 April 2020 (refer to Figure 1). The public health staff identified 863 close contacts in these 15 schools. Of the 863 close contacts, only two students have been identified as secondary cases. One of these was diagnosed by nose/throat swab testing and one had a positive antibody test 4 weeks after their exposure. A review showed that it was most likely, but not certain, that these two children were infected by transmission in the school environment.
High schools
A total of 12 COVID-19 index cases (8 students and 4 staff) were identified who had attended 10 high schools while infectious. The total number of close contacts in these 10 high schools was 598 students and 97 staff (total of 695 contacts). Nose/throat swabs were taken from one third (n=235) of contacts, all of which tested negative. In one high school, of the 75 close contacts who underwent blood testing at approximately 1 month after contact with the initial cases while infectious, only 1 student had antibodies detected, indicating infection had occurred. Overall, as shown in Figure 2, only one of 695 individuals was identified to have been infected following close contact with a school case in these 10 high schools.
Primary schools
A total of six initial cases (comprising one student and five staff) were identified in five primary schools. The total number of close contacts in these five primary schools was 137 students and 31 staff (total of 168 contacts). Nose/throat swabs were taken from one third (n=53) of contacts. Only one secondary case (nose/throat swab positive) was identified in the 168 close contacts. In the same primary school that had this secondary case, 21 close contacts underwent blood testing. The same student whose nose/throat swab tested positive also had antibodies detected through serology testing, consistent with their known recent infection. Overall, as shown in Figure 3, only one of 168 individuals was identified to have been infected following close contact with a school case in these five primary schools.
