DOSE-RESPONSE EFFECTS IN AN OUTBREAK OF SALMONELLA-ENTERITIDIS

The effects of ingested Salmonella enteritidis (SE) dose on incubation period and on the severity and duration of illness were estimated in a cohort of 169 persons who developed gastroenteritis after eating hol landaise sauce made from grade-A shell eggs. The cohort was divided in to three groups based on self-reported dose of sauce ingested. As dose increased, median incubation period decreased (37 h in the low exposu re group v. 21 h in the medium exposure group v. 17.5 h in the high ex posure group, P = 0.006) and greater proportions reported body aches ( 71. v. 85 v. 94 %, P = 0.0009) and vomiting (21 v. 58 v. 57 %, P = 000 2). Among 118 case-persons who completed a follow-up questionnaire, in creased dose was associated with increases in median weight loss in Ki lograms (3.2 v. 4.5 v. 5.0, P = 0.0001), maximum daily number of stool s (12.5 v. 15.0 v. 20.0, P = 0.02), subjective rating of illness sever ity (P = 0.0007), and the number of days of confinement to bed (3.0 v. 6.5 v. 6.5, P = 0.04). In this outbreak, ingested dose was an importa nt determinant of the incubation period, symptoms and severity of acut e salmonellosis.