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Influenza A(H3N2) Variant Virus Outbreak at Three Fairs - Maryland, 2017.

ABSTRACT: On September 17, 2017, the Maryland Department of Agriculture (MDA) was notified by fair and 4-H officials of ill swine at agricultural fair A, held September 14-17. That day, investigation of the 107 swine at fair A revealed five swine with fever and signs of upper respiratory tract illness. All five respiratory specimens collected from these swine tested positive for influenza A virus at the MDA Animal Health Laboratory, and influenza A(H3N2) virus was confirmed in all specimens by the U.S. Department of Agriculture National Veterinary Services Laboratory (NVSL). On September 18, MDA was notified by fair and 4-H officials that swine exhibitors were also ill. MDA alerted the Maryland Department of Health (MDH). A joint investigation with MDH and the local health department was started and later broadened to Maryland agricultural fairs B (September 13-17) and C (September 15-23). In total, 76 persons underwent testing for variant influenza, and influenza A(H3N2) variant (A(H3N2)v) virus infection was identified in 40 patients with exposure to swine at these fairs (Figure), including 30 (75%) who had more than one characteristic putting them at high risk for serious influenza complications; 24 (60%) of these were children aged <5 years. Twenty-six (65%) patients reported direct contact with swine (i.e., touching swine or swine enclosure), but 14 (35%) reported only indirect contact (e.g., walking through a swine barn). Two children required hospitalization; all patients recovered. This outbreak highlights the risk, particularly among children, for contracting variant influenza virus at agricultural fairs after direct or indirect swine contact. Publicizing CDC's recommendation that persons at high risk for serious influenza complications avoid pigs and swine barns might help prevent future variant influenza outbreaks among vulnerable groups (1).

SUBMITTER: Duwell MM

PROVIDER: S-EPMC6290816 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Influenza A viruses circulate in swine and can spread rapidly among swine when housed in close proximity, such as at agricultural fairs. Youth who have close and prolonged contact with influenza-infected swine at agricultural fairs may be at increased risk of acquiring influenza virus infection from swine. Animal and human health officials have issued written measures to minimize influenza transmission at agricultural exhibitions; however, there is little information on the knowledge, attitudes, and practice (KAP) of these measures among animal exhibitors. After an August 2016 outbreak of influenza A(H3N2) variant ("H3N2v") virus infections (i.e., humans infected with swine influenza viruses) in Michigan, we surveyed households of animal exhibitors at eight fairs (including one with known H3N2v infections) to assess their KAP related to variant virus infections and their support for prevention measures. Among 170 households interviewed, most (90%, 151/167) perceived their risk of acquiring influenza from swine to be low or very low. Animal exhibitor households reported high levels of behaviours that put them at increased risk of variant influenza virus infections, including eating or drinking in swine barns (43%, 66/154) and hugging, kissing or snuggling with swine at agricultural fairs (31%, 48/157). Among several recommendations, including limiting the duration of swine exhibits and restricting eating and drinking in the animal barns, the only recommendation supported by a majority of households was the presence of prominent hand-washing stations with a person to monitor hand-washing behaviour (76%, 129/170). This is a unique study of KAP among animal exhibitors and highlights that animal exhibitor households engage in behaviours that could increase their risk of variant virus infections and have low support for currently recommended measures to minimize infection transmission. Further efforts are needed to understand the lack of support for recommended measures and to encourage healthy behaviours at fairs.

Project description:Seasonal influenza epidemics are associated with high mortality and morbidity in the human population. Influenza surveillance is critical for providing information to national influenza programmes and for making vaccine composition predictions. Vaccination prevents viral infections, but rapid influenza evolution results in emerging mutants that differ antigenically from vaccine strains. Current influenza surveillance relies on Sanger sequencing of the haemagglutinin (HA) gene. Its classification according to World Health Organization (WHO) and European Centre for Disease Prevention and Control (ECDC) guidelines is based on combining certain genotypic amino acid mutations and phylogenetic analysis. Next-generation sequencing technologies enable a shift to whole-genome sequencing (WGS) for influenza surveillance, but this requires laboratory workflow adaptations and advanced bioinformatics workflows. In this study, 253 influenza A(H3N2) positive clinical specimens from the 2016-2017 Belgian season underwent WGS using the Illumina MiSeq system. HA-based classification according to WHO/ECDC guidelines did not allow classification of all samples. A new approach, considering the whole genome, was investigated based on using powerful phylogenomic tools including beast and Nextstrain, which substantially improved phylogenetic classification. Moreover, Bayesian inference via beast facilitated reassortment detection by both manual inspection and computational methods, detecting intra-subtype reassortants at an estimated rate of 15 %. Real-time analysis (i.e. as an outbreak is ongoing) via Nextstrain allowed positioning of the Belgian isolates into the globally circulating context. Finally, integration of patient data with phylogenetic groups and reassortment status allowed detection of several associations that would have been missed when solely considering HA, such as hospitalized patients being more likely to be infected with A(H3N2) reassortants, and the possibility to link several phylogenetic groups to disease severity indicators could be relevant for epidemiological monitoring. Our study demonstrates that WGS offers multiple advantages for influenza monitoring in (inter)national influenza surveillance, and proposes an improved methodology. This allows leveraging all information contained in influenza genomes, and allows for more accurate genetic characterization and reassortment detection.

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Influenza A(H3N2) Variant Virus Outbreak at Three Fairs - Maryland, 2017.

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