Table 1.

Classification and description of variables in the questionnaire collected by telephone interview in a cross-sectional study from118 Norwegian nucleus and multiplier farms.

Variable group	Variable subgroup	Variable description
Demographics	Farm details	Contact information of farmer, address, contact information of veterinarian.
Herd characteristics	Type of production	Nucleus herd (self-replacement), multiplier herd (self-replacement, purchase replacement).
	Size of production	Number of breeding animals, number of litters per herd and year, number of litters during study period of 18 months.
	Management	Farrowing system, type of batch farrowing, all in–all out practice in different stages of production.
	Trade of live animals	From nucleus herds to multipliers (replacement gilts) and commercial herds (growers or fatteners). From multipliers to commercial herds only (replacement gilts, growers or fatteners).
Health status	Pig health status	Disease status as perceived by the farmer; occurrence, severity, duration and proportion of coughing, sneezing, depression, fever, loss of appetite and/or increase in reproductive disturbances.
	Human health status	Date and occurrence of human influenza-like illness in farmer, close family, staff, veterinarian and/or visitors; confirmation on diagnosis by physician, confirmation on diagnosis by laboratory testing.
	Human vaccination	Date of vaccination against influenza A(H1N1)pdm09 in farmer, close family, staff, veterinarian and/or visitors; vaccination before or after observation of clinical signs in pigs.
Biosecurity	Live animal transport	Farmer owned vehicle, slaughterhouse owned vehicle, co-transport to/from different herds, routines of washing and disinfection of vehicles between transports (every time, occasionally, never), presence of live animals in transport vehicle on arrival at farm. Separate room for animals before loading onto transport. Separation of animals sold as live animals, or sold for slaughter. Ramp for loading animals onto transport vehicle, with at least one door closed to remaining animal housing.
	Prevention of pathogen introduction by farmer, staff, veterinarian and/or visitors	Extent and frequency of animal contact by farmer, staff, veterinarian and visitors. Design and use of physical hygiene barrier in pig house entrance; change of footwear and/or coveralls; handwashing and/or hand disinfection; disposable gloves; disposable facemask; use and duration of human quarantine after travel abroad. Alterations in any of these measures before and after influenza outbreak.
	Prevention of pathogen introduction by animals	Type, duration and extent of quarantine of introduced animals, multisite quarantine, separate ventilation, separate manure handling.