Influenza Division, National Center for Immunization and Respiratory Disease.
Clin Infect Dis. 2013 Dec;57(12):1703-12. doi: 10.1093/cid/cit649. Epub 2013 Sep 24.
Variant influenza virus infections are rare but may have pandemic potential if person-to-person transmission is efficient. We describe the epidemiology of a multistate outbreak of an influenza A(H3N2) variant virus (H3N2v) first identified in 2011.
We identified laboratory-confirmed cases of H3N2v and used a standard case report form to characterize illness and exposures. We considered illness to result from person-to-person H3N2v transmission if swine contact was not identified within 4 days prior to illness onset.
From 9 July to 7 September 2012, we identified 306 cases of H3N2v in 10 states. The median age of all patients was 7 years. Commonly reported signs and symptoms included fever (98%), cough (85%), and fatigue (83%). Sixteen patients (5.2%) were hospitalized, and 1 fatal case was identified. The majority of those infected reported agricultural fair attendance (93%) and/or contact with swine (95%) prior to illness. We identified 15 cases of possible person-to-person transmission of H3N2v. Viruses recovered from patients were 93%-100% identical and similar to viruses recovered from previous cases of H3N2v. All H3N2v viruses examined were susceptible to oseltamivir and zanamivir and resistant to adamantane antiviral medications.
In a large outbreak of variant influenza, the majority of infected persons reported exposures, suggesting that swine contact at an agricultural fair was a risk for H3N2v infection. We identified limited person-to-person H3N2v virus transmission, but found no evidence of efficient or sustained person-to-person transmission. Fair managers and attendees should be aware of the risk of swine-to-human transmission of influenza viruses in these settings.
变异流感病毒感染较为罕见，但如果人际传播效率高，可能具有大流行潜力。我们描述了 2011 年首次发现的甲型 H3N2 流感病毒（H3N2v）的多州暴发的流行病学情况。
我们确定了实验室确诊的 H3N2v 病例，并使用标准病例报告表来描述疾病和暴露情况。如果在发病前 4 天内未发现猪接触，则认为疾病是由人与人之间的 H3N2v 传播引起的。
从 2012 年 7 月 9 日至 9 月 7 日，我们在 10 个州发现了 306 例 H3N2v 病例。所有患者的中位年龄为 7 岁。常见的症状和体征包括发热（98%）、咳嗽（85%）和疲劳（83%）。16 名患者（5.2%）住院，1 例死亡。大多数感染患者在发病前报告参加过农业展览会（93%）和/或接触过猪（95%）。我们确定了 15 例可能的人与人之间传播 H3N2v 的病例。从患者中分离出的病毒与以前的 H3N2v 病例中分离出的病毒 93%-100%相同且相似。所有检查的 H3N2v 病毒均对奥司他韦和扎那米韦敏感，对金刚烷胺类抗病毒药物耐药。
在一次大暴发的变异流感中，大多数受感染的人报告了暴露情况，这表明在农业展览会上接触猪是感染 H3N2v 的危险因素。我们发现有限的人与人之间 H3N2v 病毒传播，但没有发现有效或持续的人与人之间传播的证据。展览会经理和参与者应意识到在这些环境中猪与人之间传播流感病毒的风险。
