Incubation period for outbreak-associated, non-typhoidal salmonellosis cases, Minnesota, 2000-2015

Area of Science:

• Foodborne illness research
• Infectious disease epidemiology
• Public health surveillance

Background:

• Non-typhoidal Salmonella (NTS) infections are a significant cause of foodborne illness.
• The generally reported incubation period for NTS (6-72 hours) may not accurately reflect real-world outbreak data.
• Understanding NTS incubation periods is crucial for effective outbreak investigation and control.

Purpose of the Study:

• To accurately estimate the range of incubation periods for non-typhoidal Salmonella infections based on extensive outbreak data.
• To challenge and refine the commonly accepted incubation period for NTS.

Main Methods:

• Analysis of 16 years of foodborne non-typhoidal Salmonella outbreak data from Minnesota.
• Calculation of precise incubation periods for 725 outbreak cases with sufficient data.
• Examination of variations in incubation period based on outbreak vehicle, Salmonella serotype, and setting.

Main Results:

• The median incubation period for NTS infections in this study was 45 hours.
• A significant proportion of cases (11%) had incubation periods of 12 hours or less, and 29% had periods exceeding 72 hours.
• Incubation periods varied by outbreak characteristics, with common ranges extending from 12 to 96 hours, and longer periods (up to 9 days or more) occurring.

Conclusions:

• The typical incubation period for NTS infections is broader than commonly cited, often ranging from 12 to 96 hours.
• Incubation periods longer than 96 hours are not uncommon and should be considered in public health responses.
• Further research and updated guidelines are needed to reflect the extended incubation period spectrum of NTS infections.