Incidence and Trends of Infections With Pathogens Transmitted Commonly Through Food and the Effect of Increasing Use of Culture-Independent Diagnostic Tests on Surveillance

Foodborne Diseases Active Surveillance Network, 10 U.S. Sites, 2013-2016

Ellyn P. Marder, MPH; Paul R. Cieslak, MD; Alicia B. Cronquist, MPH; John Dunn, DVM; Sarah Lathrop, PhD; Therese Rabatsky-Ehr, MPH; Patricia Ryan, MD; Kirk Smith, DVM; Melissa Tobin-D'Angelo, MD; Duc J. Vugia, MD; Shelley Zansky, PhD; Kristin G. Holt, DVM; Beverly J. Wolpert, PhD; Michael Lynch, MD; Robert Tauxe, MD; Aimee L. Geissler, PhD

Disclosures

Morbidity and Mortality Weekly Report. 2017;66(15):397-403. 

In This Article

Cases of Infection, Incidence, and Trends

During 2016, FoodNet identified 24,029 cases, 5,512 hospitalizations, and 98 deaths caused by confirmed or CIDT positive–only infections (Table 1). The largest number of confirmed or CIDT positive–only infections in 2016 was reported for Campylobacter (8,547), followed by Salmonella (8,172), Shigella (2,913), STEC (1,845), Cryptosporidium (1,816), Yersinia (302), Vibrio (252), Listeria (127), and Cyclospora (55). The proportion of infections that were CIDT positive without culture confirmation in 2016 was largest for Campylobacter (32%) and Yersinia (32%), followed by STEC (24%), Shigella (23%), Vibrio (13%), and Salmonella (8%). The overall increase in CIDT positive–only infections for these six pathogens in 2016 was 114% (range = 85%–1,432%) compared with 2013–2015. Among infections with a positive CIDT result in 2016, a reflex culture was attempted on approximately 60% at either a clinical or state public health laboratory. The proportion of attempted reflex cultures differed by pathogen, ranging from 45% for Campylobacter to 86% for STEC and 88% for Vibrio ( Figure). Among infections for which reflex culture was performed, the proportion of infections that were positive was highest for Salmonella (88%) and STEC (87%), followed by Shigella (64%), Yersinia (59%), Campylobacter (52%), and Vibrio (46%).

Figure.

Number of infections with positive culture-independent diagnostic test (CIDT) results,* by pathogen, year, and culture status — FoodNet, 10 U.S. sites, 2013–2016§
Abbreviations: FoodNet = CDC's Foodborne Diseases Active Surveillance Network; STEC = Shiga toxin–producing Escherichia coli.
*Positive CIDT results are defined as detection of the bacterial pathogen, or for STEC, Shiga toxin or the genes that encode a Shiga toxin in a stool specimen or enrichment broth using a CIDT. For STEC, only CIDT results that were positive at a state public health laboratory were counted.
Connecticut, Georgia, Maryland, Minnesota, New Mexico, Oregon, Tennessee, and selected counties in California, Colorado, and New York.
§Data for 2016 are preliminary.
For STEC, all serogroups were combined because distinguishing between serogroups using CIDTs is not possible. Shiga toxin–positive reports from clinical laboratories that were Shiga toxin–negative at a state public health laboratory were excluded (n = 568).

The incidence of confirmed infections and of confirmed or CIDT positive–only infections per 100,000 persons was highest for Campylobacter (confirmed = 11.79; confirmed or CIDT positive–only = 17.43) and Salmonella (15.40; 16.66), followed by Shigella (4.60; 5.94), Cryptosporidium (3.64; N/A**), STEC (2.85; 3.76), Yersinia (0.42; 0.62), and lowest for Vibrio (0.45; 0.51), Listeria (0.26; N/A), and Cyclospora (0.11; N/A) (Table 2). Compared with 2013–2015, the 2016 incidence of Campylobacter infection was significantly lower (11% decrease) when including only confirmed infections, yet was not significantly different when including confirmed or CIDT positive–only infections. Incidence of STEC infection was significantly higher for confirmed infections (21% increase) and confirmed or CIDT positive–only infections (43% increase). Similarly, the incidence of Yersinia infection was significantly higher for both confirmed (29% increase) and confirmed or CIDT positive–only infections (91% increase). Incidence of confirmed Cryptosporidium infection was also significantly higher in 2016 compared with 2013–2015 (45% increase).

Among 7,554 confirmed Salmonella cases in 2016, serotype information was available for 6,583 (87%). The most common serotypes were Enteritidis (1,320; 17%), Newport (797; 11%), and Typhimurium (704; 9%). The incidence in 2016 compared with 2013–2015 was significantly lower for Typhimurium (18% decrease; CI = 7%–21%) and unchanged for Enteritidis and Newport. Among 208 (95%) speciated Vibrio isolates, 103 (50%) were V. parahaemolyticus, 35 (17%) were V. alginolyticus, and 26 (13%) were V. vulnificus. Among 1,394 confirmed and serogrouped STEC cases, 503 (36%) were STEC O157 and 891 (64%) were STEC non-O157. Among 586 (70%) STEC non-O157 isolates, the most common serogroups were O26 (190; 21%), O103 (178; 20%), and O111 (106; 12%). Compared with 2013–2015, the incidence of STEC non-O157 infections in 2016 was significantly higher (26% increase; CI = 9%–46%) and the incidence of STEC O157 was unchanged.

FoodNet identified 62 cases of postdiarrheal HUS in children aged <18 years (0.56 cases per 100,000) in 2015; 33 (56%) occurred in children aged <5 years (1.18 cases per 100,000). Compared with 2012–2014, in 2015, no significant differences in incidence among all children or children aged <5 years were observed.

Excludes Shiga toxin–positive reports from clinical laboratories that were Shiga toxin–negative at a public health laboratory (n=568).
**Not applicable: all infections were confirmed.

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