Live animal markets in Minnesota: a potential source for emergence of novel influenza A viruses and interspecies transmission.

Choi MJ1, Torremorell M2, Bender JB2, Smith K3, Boxrud D3, Ertl JR2, Yang M2, Suwannakarn K2, Her D3, Nguyen J3, Uyeki TM1, Levine M1, Lindstrom S1,Katz JM1, Jhung M1, Vetter S3, Wong KK1, Sreevatsan S2, Lynfield R3.

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Abstract

BACKGROUND:

Live animal markets have been implicated in transmission of influenza A viruses (IAVs) from animals to people. We sought to characterize IAVs at two live animal markets in Minnesota to assess potential routes of occupational exposure and risk for interspecies transmission.

METHODS:

We implemented surveillance for IAVs among employees, swine, and environment (air and surfaces) during a 12-week period (October 2012-January 2013) at two markets epidemiologically associated with persons with swine-origin IAV (variant) infections. Real-time reverse transcription polymerase chain reaction (rRT-PCR), viral culture, and whole genome sequencing were performed on respiratory and environmental specimens, and serology on sera from employees at beginning and end of surveillance.

RESULTS:

Nasal swabs from 11 (65%) of 17 employees tested positive for IAVs by rRT-PCR; seven employees tested positive on multiple occasions and one employee reported influenza-like illness. Eleven (73%) of 15 employees had baseline hemagglutination-inhibition antibody titers ≥40 to swine-origin IAVs, but only one demonstrated a 4-fold titer increase to both swine-origin, and pandemic A/Mexico/4108/2009 IAVs. IAVs were isolated from swine (72/84), air (30/45) and pen railings (5/21). Whole genome sequencing of 122 IAVs isolated from swine and environmental specimens revealed multiple strains and subtype codetections. Multiple gene segment exchanges among and within subtypes were observed, resulting in new genetic constellations and reassortant viruses. Genetic sequence similarities of 99%-100% among IAVs of one market customer and swine indicated interspecies transmission.