SARS-CoV-2 outbreaks in secondary school settings in the Netherlands during fall 2020; silent circulation

BMC Infectious Diseases

Table 1 School characteristics and weekly incidence of the four schools participating in the outbreak study (n = 4)

School	Size	Weekly number of SARS-CoV-2 infections (incidence per 100,000)^a
School	Size	week 45	week 46	week 47	week 48	week 49	week 50	week 51
A	> 2000	11 (530)	7 (337)	16 (771)	17 (819)	12 (578)	5 (241)	Missing
B	700–1000	NA	NA	2 (262)	4 (524)	3 (393)	0	3 (393)
C	1500–2000	2 (118)	3 (176)	6 (352)	10 (588)	5 (294)	4 (235)	3 (176)
D	500–700	0	1 (173)	0	11 (1900)^b	5 (864)	10 (1727)	8 (1382)
Mean population incidence per 100,000		232	204	198	184	237	317	430

NA Not applicable
Highlighted in bold are the school and week where an outbreak investigation was initiated. School B enrolled in week 47 in the study. According to definition, clusters could evolve over > 1 week. Therefore the cases in bold will not add up with the number of index cases within the different clusters
^aStudents and staff combined. Numbers based on daily logs reported by the schools and excluding additional asymptomatic cases detected during our outbreak studies
^b10/11 were from the same class. Considering the extent of this outbreak, the school decided to send the entire class home and convert to online education. Consequently, no outbreak investigation could be performed

ISSN: 1471-2334