Gregory C. Gray, MD, MPH1

1
Gregory C. Gray, MD, MPH1
1 Center for Emerging Infectious Diseases,
Department of Epidemiology, University of Iowa
College of Public Health, Iowa City, IA

• Following the 2003 Netherlands poultry outbreak,
  49 of 508 poultry cullers and 64 of 63 persons
  exposed to H7N7 infected humans had serological
  evidence of H7N7 infection.1
• Swine farmers, swine veterinarians, and meat
  processing workers who handle pork had markedly
  increased odds of elevated antibodies against
  swine H1N1 and H1N2 viruses (OR 35.3,
  95CI7.7-161.8).2
• Swine workers similar risk (OR 30.3,
  95CI3.8-243.5) of elevated antibody titer to
  swine H1N1 virus was reduced almost to that of
  non-exposed controls, if the workers reported
  using gloves during their occupational
  exposures.3
• Swine influenza virus infections occurred not
  only among swine-exposed workers, but also among
  their spouses who reported no direct contact with
  swine.4
• Serological evidence was found for previous
  infections with avian H5, H6, and H7 viruses in
  US poultry-exposed veterinarians, and several
  clusters of human-to-human swine influenza virus
  infections were documented.5
• In settings where agricultural workers make up as
  much as 45 of the employed, these workers would
  increase influenza infections among community
  members by as much as 86.6

• Three interrelated arguments should be
  considered for swine and poultry workers in
  influenza control plans.
• The threat of the generation of novel viruses.
• -Facilitated by workers intense occupational
  exposure to domestic animals, reassortant viruses
  could emerge with genetic components of human,
  swine, and poultry viruses.
• The threat of workers serving as a bridging
  population to share influenza viruses across
  species.
• -Agriculture workers may introduce human
  influenza viruses to swine or introduce
  communities to swine or poultry influenza virus
  infections.
• -If they were to be infected with a virus
  efficient in human-to-human transmission,
  agricultural workers could transmit the virus to
  their families and medical care providers.
• The potential for workers to accelerate a
  pandemic in their communities.
• -In a community with a large proportion of
  swine or poultry workers working in large animal
  confinement facilities, the workers may more
  readily spread a zoonotic virus to others in
  their communities, and thus accelerate the
  epidemic and subsequent morbidity and mortality.

A series of recent cross-sectional studies have
demonstrated that persons whose occupations
involve exposure to swine and poultry may be at
increased risk of zoonotic influenza virus
infection. For instance, US swine confinement
workers had an increased odds (OR30.3, 95
CI-3.8-243.5) of having elevated antibodies
against swine H1N1 influenza virus compared to
non-swine exposed controls. Similarly, US
veterinarians who reported working with poultry
or waterfowl had an increased odds (OR17.7, 95
CI2.3-Infinity) of having elevated antibody
against H7 avian influenza virus compared to
non-poultry exposed veterinarian controls. A
recent large prospective study of 805 US swine
workers has corroborated these studies with
swine-exposed subjects (OR54.9, 95
CI13.0-232.6) and their non-swine exposed
spouses (OR28.2, 95 CI6.1-130.1) having an
increased adjusted odds of elevated antibody to
swine H1N1 influenza virus compared to
non-exposed controls. The swine-exposed workers
also had prospective evidence of swine influenza
virus infection through self-reported
influenza-like illness data, comparisons of
enrollment and follow-up sera, and the isolation
of a reassortant swine H1N1 virus from an ill
swine farmer. Such occupations may serve as a
bridging population for influenza virus spread
between animals and man. Recent influenza
modeling data have demonstrated that the intense
occupational exposures of humans working in swine
or poultry confinement buildings could facilitate
the generation of novel influenza viruses, as
well as greatly accelerate human influenza
epidemics. Swine and poultry workers should be
considered for priority receipt of pandemic
vaccines and antivirals.

• Meijer, A. Bosman, E.E. van de Kamp, B. Wilbrink,
  van Beest Holle Mdu, R. and Koopmans, M.
  Measurement of antibodies to avian influenza
  virus A (H7N7) in humans by hemagglutination
  inhibition test, J Virol Methods,
  2006132113120.
• Myers, K.P. Olsen, C.W. Setterquist, S.F.
  Capuano, A.W. Donham, K.J. and Thacker, E.L. et
  al. Are swine workers in the United States at
  increased risk of infection with zoonotic
  influenza virus?, Clin Infect Dis, 20064214-20.
  
• Ramirez, A. Capuano, A. Wellman, D. Lesher, K.
  Setterquist, S. and Gray, G. Preventing zoonotic
  influenza virus infection, J Emerg Infect Dis,
  200612997-1000.
• Gray, G. McCarthy, T. Capuano, A. Lynch, C.
  Wellman D. and Lesher K. et al. Population-based
  surveillance for zoonotic influenza A in
  agricultural workers, Program and abstracts of
  the second North American congress of
  epidemiology, Seattle (2006).
• Myers, K. Setterquist, S. Capuano, A. Gray, G.
  Infection with three avian influenza subtypes in
  US Veterinarians, Clin Infect Dis, 2007454-9.
• Saenz, R.A. Hethcote H.W. and Gray, G.C. Confined
  animal feeding operations as amplifiers of
  influenza, Vector Borne Zoonotic Dis,
  20066338-46.

• Failing to include swine and poultry workers in
  influenza prevention plans could result in
• Increased probability of generating novel
  viruses.
• Acceleration of pandemic morbidity and mortality
  among humans in rural communities.
• Reduction in protein supplies.
• Exacerbation of a pandemics tremendous economic
  impact.
• Swine and poultry workers should be included in
  influenza prevention programs
• They should receive training to reduce the
  likelihood of cross-species influenza virus
  infection.
• They should be trained to seek medical screening
  should they develop influenza-like-illness.
• The should be recognized as a priority group for
  the receipt of annual influenza vaccines,
  pandemic influenza vaccines, and pandemic use of
  antivirals.
• They should be included in increased influenza
  surveillance efforts.

Collaborators Darrell W. Trampel, James A.
Roth Funding NIH / NIAID-1 R01 AI068803-01 (Gray)

• Influenza is a zoonotic disease in which
  cross-species viral infections between domestic
  swine, avian species, and man readily occur.
• Pandemic influenza plans have given little
  attention to agricultural workers who may be at
  high risk of zoonotic influenza virus infection.