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A large COVID-19 outbreak in a high school 10 days after schools’ reopening, Israel, May 2020

Our take —

Ten days following the reopening of schools in Israel, there was an outbreak of SARS-CoV-2 infection in a high school in Jerusalem. The attack rate among students was 13.2%, and 16.8% among staff members. There were no hospitalizations, but this outbreak was caught early and represented only one school in an urban setting. These data provide critical insights into the potential for transmission among high school students and important considerations for school reopening.

Study design

Case Series

Study population and setting

In Israel, all schools were declared closed as of March 13, 2020 to prevent the spread of SARS-CoV-2. Two months later, on May 17, 2020, schools fully reopened with social distancing, use of face masks, and other risk minimization procedures in place. On May 26th and 27, 2020 (ten days after reopening), two independent COVID-19 cases were identified from an urban public school serving grades 7-12. Self-isolation of the close contacts of these students was put into place, and testing of the school community, including students, staff members, relatives, and friends, was conducted to determine the attack rate of the outbreak and describe its epidemiological characteristics. Testing was done between May 28 and May 30, 2020. Those who had not attended school since the start of reopening were excluded from testing (n=10 teachers and n=26 students); 1 additional staff member and 3 students who had attended during reopening did not receive testing.

Summary of Main Findings

A total of 153/1161 students and 25/151 staff members tested positive for COVID-19 during this period, leading to an attack rate of 13.2% among students and 16.6% among staff members. The attack rate was highest among 9th graders (32.6%, 61/187). 43% (n=66) of students and 76% (n=19) of teachers reported symptoms, including cough, headache, fever, sore throat, and myalgia. A total of 87 additional cases were reported among family members and close contacts. No hospitalizations were reported, however by 25 days, 60% of asymptomatic cases had recovered (two negative PCR results) and just 37% of symptomatic cases had recovered. Further investigation of the conditions of the school found overcrowded classrooms (average of 35-38 students), ongoing sports and dance extracurricular activities, continuous air-conditioning without open windows due to a heatwave during this period, and relaxation of the mask requirement for 3 days during the heatwave.

Study Strengths

Viral testing was done on all students, staff, and close contacts in a timely manner, including both symptomatic and asymptomatic individuals allowing for the determination of an attack rate.

Limitations

These results represent only one school in an urban setting (Jerusalem). Additionally, the median age of staff was 40 years old, but the full age distribution of the staff working at the school is not provided. Data regarding facemask use during the heatwave period were not reported, and it is difficult to determine the degree to which different components (no masks, no outside ventilation, overcrowding, sports) contributed to epidemic spread.

Value added

This is one of the first studies to quantitatively assess an outbreak of SARS-CoV-2 infection after schools reopened.

This review was posted on: 5 August 2020