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. 2024 Jul 30;10(15):e35425.
doi: 10.1016/j.heliyon.2024.e35425. eCollection 2024 Aug 15.

Clinical characteristics of COVID-19 clusters in three schools in Beijing, China: A retrospective study

Zhixia Gu  1   2   3   4 , Rui Song  1   2   4 , Yuanyuan Zhang  1   2   3   4 , Yiwei Hao  5 , Shugui Sheng  1   2   3   4 , Xiaoyou Chen  1   2   4 , Ronghua Jin  1   2   3   4
Affiliations

Clinical characteristics of COVID-19 clusters in three schools in Beijing, China: A retrospective study

Zhixia Gu et al. Heliyon. .

Abstract

Background: This retrospective analysis aims to investigate the clinical characteristics of students infected with the SARS-CoV-2 Omicron variant in three Beijing schools. Additionally, we explore the dynamic trends of nucleic acid cycle threshold values (Ct values) and serum antibody titers throughout the disease course.

Methods: Demographic, clinical, nucleic acid Ct values, and antibody titer data were collected from cases in a COVID-19 cluster in Beijing Ditan Hospital, Capital Medical University, spanning from September 6 to October 1, 2022.

Results: A total of 107 students infected with Omicron (BA.5.2 and BA.2.76) were identified across three schools. Primary clinical manifestations included fever and upper respiratory symptoms (85/107, 79.4 %), with the majority being classified as mild cases (96/107, 89.7 %). Notably, middle school students in the second school exhibited a higher peak body temperature compared to college students in the first and third schools (39.5 °C vs. 38.4 °C, adjusted P = 0.005; 39.5 °C vs. 38.6 °C, adjusted P = 0.002). Analysis of dynamic changes in Ct values revealed the lowest median Ct value in nasopharyngeal swabs on the third day of illness, reaching 35 after 9-11 days. Oropharyngeal swab nucleic acid median Ct value reached 35 approximately 3-5 days post-onset. Serum antibody detection showed continuous negativity of IgM antibody titers from days 1-10, while IgG antibody titers were positive on the first day and increased rapidly after one week.

Conclusions: The three COVID-19 cluster school outbreaks primarily resulted from Omicron infections, with no severe or fatal cases observed. Clinically, the selection of different types of SARS-CoV-2 nucleic acid swabs for virus detection can be tailored based on the infection's course.

Keywords: Antibody; Inactivated vaccine; Omicron variants; SARS-CoV-2.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1
Fig. 1
Peak body temperature distribution of febrile patients in different groups during hospitalization A. Peak body temperature in students infected with BA.5.2 (n = 41) or BA.2.76 (n = 44) omicron strains. B. Peak body temperature in students with Two (n = 29) or Three doses (n = 53) of inactivated vaccine; C. Peak body temperature in students from School No.1 (n = 41), No.2 (n = 13) or No.3 (n = 31).
Fig. 2
Fig. 2
Molecular diagnostics (Ct values) results of novel coronavirus nucleic acid detection in nasopharyngeal swabs and oropharyngeal swabs Ct value of the ORF gene (A) and N gene (B) on the 1st to 16th day after onset. If the Ct value reaches negative and the value cannot be detected, use Ct = 40 instead; The Ct value that meets discharge criteria is ≥ 35.
Fig. 3
Fig. 3
Dynamic trends of specific IgM and IgG antibody titers in patients Serological IgM (A) and IgG (B) antibody titer against SARS-CoV-2 throughout disease course. Antibody titer were transformed to logarithm scale. Criteria: Negative: ≤Log0.79(-0.102372909); Positive: ≥Log1.21(0.08278537); Suspicious: ≥ Log 0.8 (−0.096910013) and ≤ Log 1.2 (0.079181246).
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