We used data from the 90,000person Agricultural Health Study to identify 707 study subjects who were

1
Gregory C. Gray, MD, MPH,1 Troy McCarthy,1 Ana W.
Capuano, MPS, 1 Mark Lebeck,1 Sharon F.
Setterquist, MT(ASCP),1  Debbie A. Wellman,1
Christopher W. Olsen, DVM, PhD,2 Charles F.
Lynch, MD, PhD,3  Norma J. Miller,1 Patricia A.
P. Gillette, MPH,3 Kelly A. Lesher,1 Alexander I.
Klimov, PhD,4 Michael C. Alavanja, PhD,5 and
Jackie M. Katz, PhD6
1Center for Emerging Infectious Diseases, Dept.
of Epidemiology, University of Iowa College of
Public Health, Iowa City, IA 2Department of
Pathobiological Sciences, University of
Wisconsin-Madison, Madison, WI 3Department of
Epidemiology, University of Iowa College of
Public Health, Iowa City, IA 4Strain
Surveillance Section, Influenza Branch, Centers
for Disease Control and Prevention, Atlanta, GA
5National Cancer Institute, Bethesda, MD
6Immunology and Viral Pathogenesis Section,
Centers for Disease Control and Prevention,
Atlanta, GA

• 90 participated in the 12-month follow-up.
• During the fall/winter of 2005, sixteen (29) of
  54 the specimens from ILI subjects have
  yielded influenza A (15 human H3N2, 1 quadruple
  reassortant swine H1N2) and 2 (4) have
  yielded influenza B.
• After only 12 months of follow-up, the exposed
  have evidence of an increase in antibody titer
  against both swine influenza viruses that is not
  explained by antibodies to human H1 viruses
  (Table 4).

To better understand zoonotic influenza
transmission, we enrolled 803 rural Iowans in a
2-year prospective study. Demographic and
occupational risk factors were studied for
associations with antibodies against swine and
human influenza viruses using a multivariate,
proportional odds model. Upon enrollment,
swine-exposed subjects and their non-exposed
spouses had a markedly increased odds of elevated
antibody to swine influenza viruses compared to
non-exposed university controls (e.g. OR 55 95
CI 13-236 OR28 95 CI6-130 against swine
H1N1). While studies are ongoing, analysis of 658
sera pairs have demonstrated a significant
increase in the adjusted odds of having elevated
antibody to swine H1N1 and H1N2 for recently
swine-exposed (2000 to present) versus
non-exposed workers. If participants developed
influenza-like illnesses (ILI), nasal swab and
gargle samples were studied for influenza virus
using real-time polymerase chain reaction,
culture, and sequencing. In the fall/winter of
2005, sixteen of the 54 specimens from ILI
subjects yielded influenza A (15 human H3N2, 1
quadruple reassortant swine H1N2). Serological
data suggest that swine workers and their spouses
are at increased risk of zoonotic influenza virus
infections. While, currently these infections
are likely subclinical, because of their
occupational risk, swine workers should be
considered for receipt of antivirals and vaccines
in pandemic influenza planning.

• We used data from the 90,000-person Agricultural
  Health Study to identify 707 study subjects who
  were occupationally exposed to swine and/or
  poultry, and a gender and age-group matched group
  of 80 control subjects without such exposures.
• Upon enrollment, and after 12 and 24 months of
  follow-up, participants are asked to complete a
  questionnaire and to donate sera (589 AHS-E and
  69 AHS-NE).
• During the 2 years of follow-up, if a participant
  develops signs and symptoms of an influenza-like
  illness, they complete a questionnaire, provide a
  gargle sample and a nasal swab within 48 hours of
  symptom development, and ship the questionnaire
  and gargle sample to the investigators.
• Use hemagglutination inhibition and
  microneutralization procedures to examine sera.
• Hypotheses testing will be performed for any
  swine (H1, H3) or avian (H3, H4, H5, H6, H7, H9)
  influenza hemagglutinin type and later stratified
  by each swine and avian type.
• Serologic results are adjusted for antibodies to
  human influenza virus.
• To validate serological outcomes, culture and
  molecular studies will be performed on gargle and
  swab specimens to identify influenza and specific
  hemagglutinin types.

• These data suggest that swine workers are at
  increased risk of swine influenza virus
  infections.
• Swine worker spouses may also be at increased
  risk of infection through indirect contact with
  swine viruses.
• Agriculture workers should be given special
  attention in influenza surveillance strategies
  and in planning for influenza pandemics.

• Many of the non-exposed subjects were spouses of
  the exposed, and although they reported little
  swine exposure, they had lived on a swine farm
  (Table 2).
• Odds for having elevated antibodies against swine
  influenza viruses were high for the exposed and
  their non-exposed spouses compared to University
  of Iowa non-exposed controls (Table 3).

• Human-to-swine and swine-to-human influenza
  transmission have been well-documented.
• Olsen et. al. found that 23 of 74 swine farm
  workers had serologic evidence of emergent swine
  influenza infection as compared to controls (Emerg Infect Dis 20028814-9).
• Myers et. al. found farmers, meat processing
  workers, and veterinarian workers all to have
  higher odds of elevated antibodies against swine
  H1N1 and swine H1N2 influenza viruses compared to
  nonexposed controls (Clin Infect
  Dis,20064214-20).

Consultants - Kevin Knudson, PhDCEID Staff -
Whitney Baker, Mark Lebeck, Ghazi Kayali Funding
NIH / NIAID- R21 AI059214-01

• 803 rural Iowans enrolled from 29 counties
• Enrollment characteristics compared to nonexposed
  University of Iowa control group (Table 1)

Abstract revised