Format

Send to

Choose Destination
See comment in PubMed Commons below
Clin Infect Dis. 2011 Jan 1;52(1):10-8. doi: 10.1093/cid/ciq030.

Swine outbreak of pandemic influenza A virus on a Canadian research farm supports human-to-swine transmission.

Author information

  • 1University of Alberta, Edmonton, Alberta, Canada. sarah.forgie@albertahealthservices.ca

Abstract

BACKGROUND:

Swine outbreaks of pandemic influenza A (pH1N1) suggest human introduction of the virus into herds. This study investigates a pH1N1 outbreak occurring on a swine research farm with 37 humans and 1300 swine in Alberta, Canada, from 12 June through 4 July 2009.

METHODS:

The staff was surveyed about symptoms, vaccinations, and livestock exposures. Clinical findings were recorded, and viral testing and molecular characterization of isolates from humans and swine were performed. Human serological testing and performance of the human influenza-like illness (ILI) case definition were also studied.

RESULTS:

Humans were infected before swine. Seven of 37 humans developed ILI, and 2 (including the index case) were positive for pH1N1 by reverse-transcriptase polymerase chain reaction (RT-PCR). Swine were positive for pH1N1 by RT-PCR 6 days after contact with the human index case and developed symptoms within 24 h of their positive viral test results. Molecular characterization of the entire viral genomes from both species showed minor nucleotide heterogeneity, with 1 amino acid change each in the hemagglutinin and nucleoprotein genes. Sixty-seven percent of humans with positive serological test results and 94% of swine with positive swab specimens had few or no symptoms. Compared with serological testing, the human ILI case definition had a specificity of 100% and sensitivity of 33.3%. The only factor associated with seropositivity was working in the swine nursery.

CONCLUSIONS:

Epidemiologic data support human-to-swine transmission, and molecular characterization confirms that virtually identical viruses infected humans and swine in this outbreak. Both species had mild illness and recovered without sequelae.

PMID:
21148514
PMCID:
PMC3106227
DOI:
10.1093/cid/ciq030
[PubMed - indexed for MEDLINE]
Free PMC Article
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for PubMed Central
    Loading ...
    Support Center