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. 2014 Aug 7;4:5982.
doi: 10.1038/srep05982.

Transmission characteristics of different students during a school outbreak of (H1N1) pdm09 influenza in China, 2009

Ligui Wang  1 , Chenyi Chu  1 , Guang Yang  1 , Rongzhang Hao  1 , Zhenjun Li  2 , Zhidong Cao  3 , Shaofu Qiu  4 , Peng Li  4 , Zhihao Wu  4 , Zhengquan Yuan  4 , Yuanyong Xu  4 , Dajun Zeng  5 , Yong Wang  4 , Hongbin Song  4
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Transmission characteristics of different students during a school outbreak of (H1N1) pdm09 influenza in China, 2009

Ligui Wang et al. Sci Rep. .
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Abstract

Many outbreaks of A(H1N1)pdm09 influenza have occurred in schools with a high population density. Containment of school outbreaks is predicted to help mitigate pandemic influenza. Understanding disease transmission characteristics within the school setting is critical to implementing effective control measures. Based on a school outbreak survey, we found almost all (93.7%) disease transmission occurred within a single grade, only 6.3% crossed grades. Transmissions originating from freshmen exhibited a star-shaped network; other grades exhibited branch- or line-shaped networks, indicating freshmen have higher activity and are more likely to cause infection. R0 for freshmen, calculated as 2.04, estimated as 2.76, was greater than for other grades (P < 0.01). Without intervention, the estimated number of cases was much greater when the outbreak was initiated by freshmen than by other grades. Furthermore, the estimated number of cases required to be under quarantine and isolation for freshmen was less than that of equivalent other grades. So we concluded that different grades have different transmission mode. Freshmen were the main facilitators of the spread of A(H1N1)pdm09 influenza during this school outbreak, so control measures (e.g. close contact isolation) priority used for freshmen would likely have effectively reduced spread of influenza in school settings.

Figures

Figure 1. Number of confirmed H1N1 cases in four grades based on the illness onset.
Figure 2. Disease transmission among confirmed cases.
(a) Disease transmission between confirmed cases. Red ellipse: freshmen, yellow box: sophomores, green diamond: juniors, blue triangle: seniors. The numbers means illness onset, 1 refers to August 27, 2 refers to August 28, and so forth. (b) The disease transmission across the grades. I: freshmen, II: sophomores, III: juniors, and IV: seniors.
Figure 3. Comparison of actual R0 values for different grades.
† single factor analysis of variance (P < 0.01), the median of actual R0 values for freshmen is 2, and is 1 for other grades.
Figure 4. Estimated numbers of cases of A(H1N1)pdm09 when no control measures are used to control the outbreak, varying the source of the index case.
The model shows predicted cases if the outbreak was initiated by a freshman, sophomore, junior, or senior, respectively.
Figure 5. Estimated numbers of cases under quarantine and isolation of equal freshmen, sophomores, juniors, or seniors over the first 20 days of the outbreak, if the outbreak was initiated by freshman.
(a), quarantine and isolation of 25% freshmen, sophomores, juniors, or seniors on the first day of outbreak; (b), quarantine of 50% freshmen, sophomores, juniors, or seniors on the first day of outbreak; (c), quarantine of 75% freshmen, sophomores, juniors, or seniors on the first day of outbreak; (d), quarantine of 25% freshmen, sophomores, juniors, or seniors on the second day of outbreak; (e), quarantine of 50% freshmen, sophomores, juniors, or seniors on the second day of outbreak; (f), quarantine of 75% freshmen, sophomores, juniors, or seniors on the second day of outbreak; (g), quarantine of 25% freshmen, sophomores, juniors, or seniors on the third day of outbreak; (h), quarantine of 50% freshmen, sophomores, juniors, or seniors on the third day of outbreak; (i), quarantine of 75% freshmen, sophomores, juniors, or seniors on the third day of outbreak; (j), quarantine of 25% freshmen, sophomores, juniors, or seniors on the fourth day of outbreak; (k), quarantine of 50% freshmen, sophomores, juniors, or seniors on the fourth day of outbreak; (l), quarantine of 75% freshmen, sophomores, juniors, or seniors on the fourth day of outbreak; (m), quarantine of 25% freshmen, sophomores, juniors, or seniors on the fifth day of outbreak; (n), quarantine of 50% freshmen, sophomores, juniors, or seniors on the fifth day of outbreak; (o), quarantine of 75% freshmen, sophomores, juniors, or seniors on the fifth day of outbreak.
Figure 6. The transmission dynamics model of A(H1N1)pdm09 influenza among students attending a college in northern China.
† i = 1,2,3,4, j = 1,2,3,4, i ≠ j. ‡Each grade was divided into four groups (Susceptible, Exposed, Infected and Removed).
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