Incubation periods of enteric illnesses in foodborne outbreaks, United States, 1998-2013

Abstract

Early in a foodborne disease outbreak investigation, illness incubation periods can help focus case interviews, case definitions, clinical and environmental evaluations and predict an aetiology. Data describing incubation periods are limited. We examined foodborne disease outbreaks from laboratory-confirmed, single aetiology, enteric bacterial and viral pathogens reported to United States foodborne disease outbreak surveillance from 1998-2013. We grouped pathogens by clinical presentation and analysed the reported median incubation period among all illnesses from the implicated pathogen for each outbreak as the outbreak incubation period. Outbreaks from preformed bacterial toxins (Staphylococcus aureus, Bacillus cereus and Clostridium perfringens) had the shortest outbreak incubation periods (4-10 h medians), distinct from that of Vibrio parahaemolyticus (17 h median). Norovirus, salmonella and shigella had longer but similar outbreak incubation periods (32-45 h medians); campylobacter and Shiga toxin-producing Escherichia coli had the longest among bacteria (62-87 h medians); hepatitis A had the longest overall (672 h median). Our results can help guide diagnostic and investigative strategies early in an outbreak investigation to suggest or rule out specific etiologies or, when the pathogen is known, the likely timeframe for exposure. They also point to possible differences in pathogenesis among pathogens causing broadly similar syndromes.

Keywords: Epidemiology; food-borne infections; outbreaks.

Fig. 1.

Example of redistribution of reported outbreak incubation periods* for foodborne outbreaks caused by Campylobacter spp. from dataset including days to dataset including only hours – Foodborne Disease Outbreak Surveillance System, 1998–2013. *Reported median of illness incubation periods within an outbreak.

Fig. 2.

Distribution with median and 15^th to 85^th percentiles of reported outbreak incubation periods* of foodborne outbreaks caused by the four most commonly reported serotypes of Salmonella enterica, United States – Foodborne Disease Outbreak Surveillance System, 1998–2013. *Reported median of illness incubation periods within an outbreak.

Fig. 3.

Distribution with median and 15^th to 85^th percentiles of reported outbreak incubation periods* in foodborne outbreaks by aetiology, United States – Foodborne Disease Outbreak Surveillance System, 1998–2013. *Reported median of illness incubation periods within an outbreak.