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Be Sure You're Helping Guard Against The Current Strains of Flu

It's An Evolving Organism

Once a single, stable H1N1 subtype, the influenza A virus in swine (IAV-S) is genetically changing and transmitting at a rapidly increasing pace. Understanding how a single, stable IAV-S subtype evolved into multiple subtypes is critical to controlling the virus.

New Strains Means Herds With Pre-Existing Immunity Aren't Protected

The prevalent influenza virus strains menacing swine production have evolved as new subtypes and clusters of H1N1, H1N2 and H3N2, which means the virus can spread rapidly through herds, even with pre-existing immunity.1

Prevalence of IAV-S strains
IAVS strains pie chart

The 3 most common clusters2:

  • H1N1 Gamma
  • H1N2 Delta-1
  • H3N2 Cluster IV-A

H3N2 Clusters IV-A and IV-B have risen in importance of viruses circulating in U.S. swine today.2

  • Influenza outbreaks at agricultural fairs traced to the H3N2 human variant virus H3N2v.3
  • 309 reported H3N2v cases caused one death and 16 hospitalizations.3
  • Multistate outbreaks occurred in summer 2012.3

Disease Is Present, Even When There Are No Clinical Signs4

Regardless of the farm type, age of pigs or time of year, disease can be present in pigs, even when there are no clinical signs.4 Ongoing surveillance is critical. Zoetis works closely with universities and veterinary diagnostic laboratories to evaluate which strains are impacting the industry now and those that may become problematic in the future.

91% Graph

Surveillance shows that 91% of farms enrolled in a 2009-2011 study tested positive for influenza at least once.4,5


  1. Sandbulte MR, Spickler AR, Zaabel PK, Roth JA. Optimal use of vaccines for control of influenza A virus in swine. Vaccines. 2015;3(1):22-73.
  2. Veterinary Services, Animal and Plant Health Inspection Services, US Department of Agriculture. Influenza A Virus in Swine Surveillance: Fiscal Year 2015 Quarterly Report; Surveillance Summary for Fourth Quarter FY 2015. Published February 2016. https://www.aphis.usda.gov/animal_health/animal_dis_spec/swine/downloads/fy2015quarter4swinereport.pdf. Accessed April 9, 2017.
  3. Centers for Disease Control and Prevention. First H3N2v Outbreak of 2013 Reported; CDC Continues to Urge High Risk People to Avoid Swine at Fairs, 2013. http://www.cdc.gov/flu/spotlights/h3n2v-firstcases-2013.htm. Accessed April 9, 2017.
  4. Corzo C, Gramer M, Lowe J, Webby R. Swine influenza active surveillance in the United States, in Proceedings. 6th Inter Symp Emerg Re-emerg Pig Dis 2011;Abstract 30.
  5. Allerson M, Torremorell M. Influenza virus prevalence and risk factors in weaning-age pigs, in Proceedings. Allen D. Leman Swine Conf 2013;40:97.