Pittman Ratterree Dana C, Chitlapilly Dass Sapna, Ndeffo-Mbah Martial L
Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, United States.
Department of Animal Science, College of Agriculture and Life Sciences, Texas A&M University, College Station, TX, United States.
Front Vet Sci. 2025 Apr 1;12:1523981. doi: 10.3389/fvets.2025.1523981. eCollection 2025.
Agricultural fairs offer a unique interface between humans and swine. We investigate the transmissibility of influenza A variant from pigs to humans using epidemiological data from a 2011 zoonotic outbreak of an influenza H3N2 variant during an agricultural county fair in Pennsylvania.
We developed a mathematical model for the transmission of a swine influenza pathogen among pigs and humans at an agricultural fair. We fitted our model to the outbreak data to estimate zoonotic transmissibility. We considered nine data-driven scenarios of swine-to-swine basic reproductive number (R) and the number of infected pigs at the start of the fair, and we simulated the zoonotic outbreak dynamics.
We estimated the probability of swine-to-human H3N2v transmission per minute of swine contact for which our model best fitted the data. The probability of transmission of H3N2v per minute of contact with swine among club members was estimated to vary from 0.029 (95% confidence interval (CI): 0.028-0.030), when R = 2 with 1 initially infected pig, to 0.00099 (0.00095-0.00102), when R = 6 with 5 initially infected pigs. For attendees, we showed that the probability equals 0.0168 (95% CI: 0.0167-0.0169), when R = 2 with 1 initially infected pig, and 0.00371 (95% CI: 0.00368-0.00373), when R = 2 with 5 initially infected pigs. For all scenarios, we estimated H3N2v infection prevalence among club members and attendees to average 12 and 0.7%, respectively.
These results show that the transmission risk may vary substantially between club members and attendees and with the underlying disease transmission among pigs. Although fair attendees may have a small transmissibility risk, annual fair attendees represent a large population likely to experience zoonotic events and facilitate the emergence of a potential pandemic influenza variant.
农贸会提供了人类与猪之间独特的接触界面。我们利用宾夕法尼亚州一个农业县集市上2011年H3N2变异株人畜共患病爆发的流行病学数据，研究甲型流感变异株从猪传播给人的情况。
我们建立了一个数学模型，用于描述猪流感病原体在农贸会上猪与人之间的传播。我们将模型与爆发数据拟合，以估计人畜共患传播率。我们考虑了猪与猪之间基本繁殖数（R）和集市开始时感染猪数量的九种数据驱动情景，并模拟了人畜共患疾病爆发动态。
我们估计了模型最适合数据时，猪与人之间H3N2v传播每分钟的概率。俱乐部成员中，与猪接触每分钟H3N2v传播的概率估计值在R = 2且最初有1头感染猪时为0.029（95%置信区间（CI）：0.028 - 0.030），到R = 6且最初有5头感染猪时为0.00099（0.00095 - 0.00102）之间变化。对于参会者，我们发现当R = 2且最初有1头感染猪时，该概率等于0.0168（95% CI：0.0167 - 0.0169），当R = 2且最初有5头感染猪时为0.00371（95% CI：0.00368 - 0.00373）。在所有情景中，我们估计俱乐部成员和参会者中H3N2v感染患病率平均分别为12%和0.7%。
这些结果表明，俱乐部成员和参会者之间的传播风险可能有很大差异，且与猪之间潜在的疾病传播情况有关。尽管集市参会者的传播风险可能较小，但每年的集市参会者构成了一个庞大群体，他们可能经历人畜共患事件，并促使潜在的大流行性流感变异株出现。
