A tradition and an epidemic : determinants of the campylobacteriosis winter peak in Switzerland

Campylobacteriosis is the most frequently reported food borne infection in Switzerland. We investigated determinants of infections and illness experience in wintertime. A case-control study was conducted in Switzerland between December 2012 and February 2013. Cases were recruited among laboratory-confirmed campylobacteriosis patients. Population-based controls were matched according to age group, sex and canton of residence. We determined risk factors associated with campylobacteriosis, and help seeking behaviour and illness perception. The multivariable analysis identified two factors associated with an increased risk for campylobacteriosis: consumption of meat fondue (matched odds ratio [mOR] 4.0, 95 % confidence interval [CI] 2.3-7.1) and travelling abroad (mOR 2.7, 95 % CI 1.1-6.4). Univariable analysis among meat fondue consumers revealed chicken as the type of meat with the highest risk of disease (mOR 3.8, 95 % CI 1.1-13.5). Most frequently reported signs and symptoms among patients were diarrhoea (98 %), abdominal pain (81 %), fever (66 %), nausea (44 %) and vomiting (34 %). The median perceived disease severity was 8 on a 1-to-10 rating scale. Patients reported a median duration of illness of 7 days and 14 % were hospitalised. Meat fondues, mostly "Fondue chinoise", traditionally consumed during the festive season in Switzerland, are the major driver of the epidemic campylobacteriosis peak in wintertime. At these meals, individual handling and consumption of chicken meat may play an important role in disease transmission. Laboratory-confirmed patients are severely ill and hospitalisation rate is considerable. Public health measures such as decontamination of chicken meat and improved food handling behaviour at the individual level are urgently needed.