title: Outbreak of Rift Valley fever affecting veterinarians and farmers in South Africa, 2008.
abstract: BACKGROUND
  During 2008, Rift Valley fever (RVF) virus re-emerged in South Africa as focal outbreaks in several provinces.
  
  
  OBJECTIVE
  To investigate an outbreak affecting cattle farmers and farm workers, and the staff and students of a veterinary school, assess the prevalence of infection during the outbreak, document the clinical presentation of cases, and identify potential risk factors.
  
  
  METHODS
  We conducted a cross-sectional serological survey of exposed veterinarians and farmers, who were examined to determine the presence of current or recent illness. Blood specimens were collected for virus isolation, nucleic acid detection and serology. A subset was interviewed using a standardised questionnaire to obtain data on recent exposures and risk factors for infection.
  
  
  RESULTS
  Of 53 participants potentially exposed to infected domestic ruminants, 15% had evidence of recent infection and 4% evidence of past exposure to the RVF virus. The prevalence of acute infection was 21% in veterinarians compared with 9% in farmers and farm workers. After a mean incubation period of 4.3 days, the most frequent symptoms experienced included myalgia (100%), headache (88%) and malaise (75%). No asymptomatic cases were identified. Transmission, by direct contact with infected animals was the major risk factor in these professional groups. Performing animal autopsies was significantly associated with acute infection (risk ratio 16.3, 95% confidence interval 2.3 - 114.2).
  
  
  CONCLUSIONS
  Increased risks associated with veterinary practices highlight a need for the use of personal protective equipment, and identify veterinarians as a primary target group for future vaccination.
authors.affiliation: Outbreak Response Unit, National Institute for Communicable Diseases (NICD) of the National Health Laboratory Service (NHLS), Sandringham, Johannesburg. bretta@nicd.ac.za
authors.forename: Brett N
authors.initials: BN
authors.lastname: Archer
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Weyer
authors.forename: Janusz
authors.initials: J
authors.lastname: Paweska
authors.forename: Deliwe
authors.initials: D
authors.lastname: Nkosi
authors.forename: Patricia
authors.initials: P
authors.lastname: Leman
authors.forename: Khin San
authors.initials: KS
authors.lastname: Tint
authors.forename: Lucille
authors.initials: L
authors.lastname: Blumberg
mesh_terms: D000382:Agricultural Workers' Diseases / Q000453:epidemiology*; D004196:Disease Outbreaks; D006801:Humans; D008111:Liver Function Tests; D009784:Occupational Diseases / Q000453:epidemiology*; D012295:Rift Valley Fever / Q000453:epidemiology*; D012307:Risk Factors; D013019:South Africa / Q000453:epidemiology; D018634:Veterinarians