Short Communication Serological and molecular prevalence of swine influenza virus on farms in northwestern Mexico Guadalupe Lo ´ pez-Robles, Maricela Montalvo-Corral, Alexel Burgara-Estrella, Jesu ´s Herna ´ ndez * Laboratorio de Inmunologı´a, Centro de Investigacio ´n en Alimentacio ´n y Desarrollo, A.C., Km 0.6, Carretera a la Victoria, 83000 Hermosillo, Sonora, Mexico 1. Introduction Swine influenza virus (SIV) belongs to the Orthomyx- oviridae family and contains 8 segments of single-stranded, negative-sense RNA, encoding 11 proteins. Hemagglutinin (HA) and neuraminidase (NA) are surface viral proteins that provide a capability for virus selection, recognition, propagation, and antigenicity and are targets for diagnostic tests (Thacker and Janke, 2008). Swine influenza is a seasonal respiratory disease that is easily spread among pigs, is distributed worldwide and is economically impor- tant. SIV is a primary agent that may allow entry of other pathogens into the host (Easterday and Van Reeth, 2006). It also represents a zoonotic risk for people who are in close contact with pigs (Gray et al., 2007; Lopez-Robles et al., 2012). In early 2009, a swine-origin virus of the H1N1 subtype caused an influenza pandemic that reached level 6 and spread rapidly among humans (WHO, 2009). This novel influenza virus was detected by the CDC in samples from the USA, Mexico and Canada at the same time (Dawood et al., 2009). Unfortunately, no genetic data on SIV in Mexico had been reported prior to the outbreak. After the pandemic, an influenza virus isolated from swine in Mexico was analyzed and was found to be phylogenetically Veterinary Microbiology 172 (2014) 323–328 A R T I C L E I N F O Article history: Received 22 August 2013 Received in revised form 9 May 2014 Accepted 12 May 2014 Keywords: Swine influenza H1N1 H3N2 Survey Swine A B S T R A C T The aim of this study was to provide an overview of the epidemiological status of swine influenza viruses in pigs from northwestern Mexico in 2008–2009. A serological and molecular survey was conducted in 150 pigs from 15 commercial farms in Sonora, Mexico (northwestern region of Mexico). The serological data showed that 55% of the sera were positive for the H1N1 subtype, 59% for the H3N2 subtype, and 38% for both subtypes. Overall, 16.6% (25/150) of the samples were positive for type A influenza by qRT-PCR. The phylogenetic analysis of the H1 viruses circulating in northwestern Mexico were grouped into cluster a, from five other clusters previously described. The influenza virus H1 circulating in northwestern Mexico showed 97–100% identity at the nucleotide level among them, 89% identity with other North American strains, 88% with strains from central Mexico, and 85% with the pandemic A/H1N1p2009 virus. Meanwhile, a closer relationship with some influenza viruses from North America (97% nucleotide identity) was found for H3 subtype. In conclusion, our results demonstrated a high circulation of strains similar to those observed in the North American linage among commercial farms in northwestern Mexico, involving of a different lineage virus different to the influenza pandemic of 2009. ß 2014 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +52 662 2800010; fax: +52 662 2892400x294. E-mail address: jhdez@ciad.mx (J. Herna ´ ndez). Contents lists available at ScienceDirect Veterinary Microbiology jo u rn al ho m epag e: ww w.els evier.c o m/lo cat e/vetmic http://dx.doi.org/10.1016/j.vetmic.2014.05.017 0378-1135/ß 2014 Elsevier B.V. All rights reserved.