Alicia Cronquist

Salmonellosis Outcomes Differ Substantially by Serotype

BACKGROUND Most human infections are caused by closely related serotypes within 1 species of Salmonella. Few data are available on differences in severity of disease among common serotypes. METHODS We examined data from all cases of Salmonella infection in FoodNet states during 1996-2006. Data included serotype, specimen source, hospitalization, and outcome. RESULTS Among 46,639 cases, 687 serotypes were identified. Overall, 41,624 isolates (89%) were from stool specimens, 2524 (5%) were from blood, and 1669 (4%) were from urine; 10,393 (22%) cases required hospitalization, and death occurred in 219 (0.5%). The case fatality rate for S. Newport (0.3%) was significantly lower than for Typhimurium (0.6%); Dublin (3.0%) was higher. With respect to invasive disease, 13 serotypes had a significantly higher proportion than Typhimurium (6%), including Enteritidis (7%), Heidelberg (13%), Choleraesuis (57%), and Dublin (64%); 13 serotypes were significantly less likely to be invasive. Twelve serotypes, including Enteritidis (21%) and Javiana (21%), were less likely to cause hospitalization than Typhimurium (24%); Choleraesuis (60%) was significantly more so. CONCLUSIONS Salmonella serotypes are closely related genetically yet differ significantly in their pathogenic potentials. Understanding the mechanisms responsible for this may be key to a more general understanding of the invasiveness of intestinal bacterial infections.

Increased Recognition of Non-O157 Shiga Toxin–Producing Escherichia coli Infections in the United States During 2000–2010: Epidemiologic Features and Comparison with E. coli O157 Infections

BACKGROUND Shiga toxin-producing Escherichia coli (STEC) are an important cause of diarrhea and the major cause of postdiarrheal hemolytic uremic syndrome. Non-O157 STEC infections are being recognized with greater frequency because of changing laboratory practices. METHODS Foodborne Diseases Active Surveillance Network (FoodNet) site staff conducted active, population-based surveillance for laboratory-confirmed STEC infections. We assessed frequency and incidence of STEC infections by serogroup and examined and compared demographic factors, clinical characteristics, and frequency of international travel among patients. RESULTS During 2000-2010, FoodNet sites reported 2006 cases of non-O157 STEC infection and 5688 cases of O157 STEC infections. The number of reported non-O157 STEC infections increased from an incidence of 0.12 per 100,000 population in 2000 to 0.95 per 100,000 in 2010; while the rate of O157 STEC infections decreased from 2.17 to 0.95 per 100,000. Among non-O157 STEC, six serogroups were most commonly reported: O26 (26%), O103 (22%), O111 (19%), O121 (6%), O45 (5%), and O145 (4%). Non-O157 STEC infections were more common among Hispanics, and infections were less severe than those caused by O157 STEC, but this varied by serogroup. Fewer non-O157 STEC infections were associated with outbreaks (7% versus 20% for O157), while more were associated with international travel (14% versus 3% for O157). CONCLUSIONS Improved understanding of the epidemiologic features of non-O157 STEC infections can inform food safety and other prevention efforts. To detect both O157 and non-O157 STEC infections, clinical laboratories should routinely and simultaneously test all stool specimens submitted for diagnosis of acute community-acquired diarrhea for O157 STEC and for Shiga toxin and ensure that isolates are sent to a public health laboratory for serotyping and subtyping.

Multistate outbreak of listeriosis associated with cantaloupe.

BACKGROUND Although new pathogen-vehicle combinations are increasingly being identified in produce-related disease outbreaks, fresh produce is a rarely recognized vehicle for listeriosis. We investigated a nationwide listeriosis outbreak that occurred in the United States during 2011. METHODS We defined an outbreak-related case as a laboratory-confirmed infection with any of five outbreak-related subtypes of Listeria monocytogenes isolated during the period from August 1 through October 31, 2011. Multistate epidemiologic, trace-back, and environmental investigations were conducted, and outbreak-related cases were compared with sporadic cases reported previously to the Listeria Initiative, an enhanced surveillance system that routinely collects detailed information about U.S. cases of listeriosis. RESULTS We identified 147 outbreak-related cases in 28 states. The majority of patients (127 of 147, 86%) were 60 years of age or older. Seven infections among pregnant women and newborns and one related miscarriage were reported. Of 145 patients for whom information about hospitalization was available, 143 (99%) were hospitalized. Thirty-three of the 147 patients (22%) died. Patients with outbreak-related illness were significantly more likely to have eaten cantaloupe than were patients 60 years of age or older with sporadic illness (odds ratio, 8.5; 95% confidence interval, 1.3 to ∞). Cantaloupe and environmental samples collected during the investigation yielded isolates matching all five outbreak-related subtypes, confirming that whole cantaloupe produced by a single Colorado farm was the outbreak source. Unsanitary conditions identified in the processing facility operated by the farm probably resulted in contamination of cantaloupes with L. monocytogenes. CONCLUSIONS Raw produce, including cantaloupe, can serve as a vehicle for listeriosis. This outbreak highlights the importance of preventing produce contamination within farm and processing environments.

Invasive Listeriosis in the Foodborne Diseases Active Surveillance Network (FoodNet), 2004–2009: Further Targeted Prevention Needed for Higher-Risk Groups

BACKGROUND Listeriosis can cause severe disease, especially in fetuses, neonates, older adults, and persons with certain immunocompromising and chronic conditions. We summarize US population-based surveillance data for invasive listeriosis from 2004 through 2009. METHODS We analyzed Foodborne Diseases Active Surveillance Network (FoodNet) data for patients with Listeria monocytogenes isolated from normally sterile sites. We describe the epidemiology of listeriosis, estimate overall and specific incidence rates, and compare pregnancy-associated and nonpregnancy-associated listeriosis by age and ethnicity. RESULTS A total of 762 listeriosis cases were identified during the 6-year reporting period, including 126 pregnancy-associated cases (17%), 234 nonpregnancy-associated cases(31%) in patients aged <65 years, and 400 nonpregnancy-associated cases (53%) in patients aged ≥ 65 years. Eighteen percent of all cases were fatal. Meningitis was diagnosed in 44% of neonates. For 2004-2009, the overall annual incidence of listeriosis varied from 0.25 to 0.32 cases per 100,000 population. Among Hispanic women, the crude incidence of pregnancy-associated listeriosis increased from 5.09 to 12.37 cases per 100,000 for the periods of 2004-2006 and 2007-2009, respectively; among non-Hispanic women, pregnancy-associated listeriosis increased from 1.74 to 2.80 cases per 100,000 for the same periods. Incidence rates of nonpregnancy-associated listeriosis in patients aged ≥ 65 years were 4-5 times greater than overall rates annually. CONCLUSIONS Overall listeriosis incidence did not change significantly from 2004 through 2009. Further targeted prevention is needed, including food safety education and messaging (eg, avoiding Mexican-style cheese during pregnancy). Effective prevention among pregnant women, especially Hispanics, and older adults would substantially affect overall rates.

A population-based estimate of the substantial burden of diarrhoeal disease in the United States; FoodNet, 1996-2003

From 1996 to 2003, four 12-month population-based surveys were performed in FoodNet sites to determine the burden of diarrhoeal disease in the population. Acute diarrhoeal illness (ADI) was defined as > or =3 loose stools in 24 hours with impairment of daily activities or duration of diarrhoea >1 day. A total of 52840 interviews were completed. The overall weighted prevalence of ADI in the previous month was 5.1% (95% CI+/-0.3%), corresponding to 0.6 episodes of ADI per person per year. The average monthly prevalence of ADI was similar in each of the four survey cycles (range 4.5-5.2%). Rates of ADI were highest in those age <5 years. Of those with ADI, 33.8% (95% CI+/-2.7%) reported vomiting, 19.5% (95% CI+/-2.1%) visited a medical provider, and 7.8% (95% CI+/-1.4%) took antibiotics. Rates of ADI were remarkably consistent over time, and demonstrate the substantial burden placed on the health-care system.

Estimates of Enteric Illness Attributable to Contact With Animals and Their Environments in the United States

BACKGROUND Contact with animals and their environment is an important, and often preventable, route of transmission for enteric pathogens. This study estimated the annual burden of illness attributable to animal contact for 7 groups of pathogens: Campylobacter species, Cryptosporidium species, Shiga toxin-producing Escherichia coli (STEC) O157, STEC non-O157, Listeria monocytogenes, nontyphoidal Salmonella species, and Yersinia enterocolitica. METHODS By using data from the US Foodborne Diseases Active Surveillance Network and other sources, we estimated the proportion of illnesses attributable to animal contact for each pathogen and applied those proportions to the estimated annual number of illnesses, hospitalizations, and deaths among US residents. We established credible intervals (CrIs) for each estimate. RESULTS We estimated that 14% of all illnesses caused by these 7 groups of pathogens were attributable to animal contact. This estimate translates to 445 213 (90% CrI, 234 197-774 839) illnesses annually for the 7 groups combined. Campylobacter species caused an estimated 187 481 illnesses annually (90% CrI, 66 259-372 359), followed by nontyphoidal Salmonella species (127 155; 90% CrI, 66 502-219 886) and Cryptosporidium species (113 344; 90% CrI, 22 570-299 243). Of an estimated 4933 hospitalizations (90% CrI, 2704-7914), the majority were attributable to nontyphoidal Salmonella (48%), Campylobacter (38%), and Cryptosporidium (8%) species. Nontyphoidal Salmonella (62%), Campylobacter (22%), and Cryptosporidium (9%) were also responsible for the majority of the estimated 76 deaths (90% CrI, 5-211). CONCLUSIONS Animal contact is an important transmission route for multiple major enteric pathogens. Continued efforts are needed to prevent pathogen transmission from animals to humans, including increasing awareness and encouraging hand hygiene.

Reduction in the Incidence of Invasive Listeriosis in Foodborne Diseases Active Surveillance Network Sites, 1996-2003

BACKGROUND Listeriosis is a leading cause of death among patients with foodborne diseases in the United States. Monitoring disease incidence is an important element of listeriosis surveillance and control. METHOD We conducted population-based surveillance for Listeria monocytogenes isolates obtained from normally sterile sites at all clinical diagnostic laboratories in the Foodborne Diseases Active Surveillance Network from 1996 through 2003. RESULTS The incidence of laboratory-confirmed invasive listeriosis decreased by 24% from 1996 through 2003; pregnancy-associated disease decreased by 37%, compared with a decrease of 23% for patients > or =50 years old. The highest incidence was reported among Hispanic persons from 1997 through 2001. Differences in incidence by age group and ethnicity may be explained by dietary preferences. CONCLUSION The marked decrease in the incidence of listeriosis may be related to the decrease in the prevalence of L. monocytogenes contamination of ready-to-eat foods since 1996. The crude incidence in 2003 of 3.1 cases per 1 million population approaches the governments Healthy People objective of 2.5 cases per 1 million population by 2005. Further decreases in listeriosis incidence will require continued efforts of industry and government to reduce contamination of food and continued efforts to educate consumers and clinicians.

The Evolving Epidemiology of Hepatitis A in the United States: Incidence and Molecular Epidemiology From Population-Based Surveillance, 2005-2007

BACKGROUND The incidence of hepatitis A virus (HAV) disease is the lowest ever in the United States. We describe recent incidence and characteristics of cases of HAV disease from 6 US sites conducting hepatitis surveillance in the Emerging Infections Program. METHODS Health departments conducted enhanced, population-based surveillance for HAV from 2005 through 2007. Demographic and risk factor data were collected on suspected cases (persons with a positive IgM anti-HAV result) using a standard form. Remnant serum specimens from a convenience sample of cases were tested by polymerase chain reaction, followed by sequencing the 315-nucleotide segment of the VP1-P2B junction. RESULTS There were 1156 HAV cases reported during 2005 through 2007. The combined population under surveillance was 29.8 million in 2007. The overall annual incidence rate was 1.3 per 100 000 population (range by site, 0.7-2.3). Of reported cases, 53.4% were male, 42.4% were white, 44.7% were aged 15 to 39 years, and 91.4% resided in urban areas. Reported risk factors were international travel (45.8%), contact with a case (14.8%), employee or child in a daycare center (7.6%), exposure during a food or waterborne common-source outbreak (7.2%), illicit drug use (4.3%), and men who had sex with men (3.9%). Genotypes among the 271 case specimens were IA (87.8%), IB (11.4%), and IIIA (0.7%). Of the 271 polymerase chain reaction-positive specimens, 131 (48.3%) were from cases reporting travel or exposure to a traveler; 58 of the 131 cases reported travel to Mexico, and 53 of the 58 were within the US-IA(1) cluster. CONCLUSIONS International travel was the predominant risk factor for HAV transmission. Health care providers should encourage vaccination of at-risk travelers.

Travel-associated enteric infections diagnosed after return to the United States, Foodborne Diseases Active Surveillance Network (FoodNet), 2004-2009.

BACKGROUND Approximately 40% of US travelers to less developed countries experience diarrheal illness. Using data from the Foodborne Diseases Active Surveillance Network (FoodNet), we describe travel-associated enteric infections during 2004-2009, characterizing the patients, pathogens, and destinations involved. METHODS FoodNet conducts active surveillance at 10 US sites for laboratory-confirmed infections with 9 pathogens transmitted commonly through food. Travel-associated infections are infections diagnosed in the United States but likely acquired abroad based on a pathogen-specific time window between return from international travel to diagnosis. We compare the demographic, clinical, and exposure-related characteristics of travelers with those of nontravelers and estimate the risk of travel-associated infections by destination, using US Department of Commerce data. RESULTS Of 64,039 enteric infections reported to FoodNet with information about travel, 8270 (13%) were travel associated. The pathogens identified most commonly in travelers were Campylobacter (42%), nontyphoidal Salmonella (32%), and Shigella (13%). The most common travel destinations were Mexico, India, Peru, Dominican Republic, and Jamaica. Most travel-associated infections occurred in travelers returning from Latin America and the Caribbean (LAC). Risk was greatest after travel to Africa (75.9 cases per 100,000 population), followed by Asia (22.7 cases per 100,000), and LAC (20.0 cases per 100,000). CONCLUSIONS The Latin America and Caribbean region accounts for most travel-associated enteric infections diagnosed in the United States, although travel to Africa carries the greatest risk. Although FoodNet surveillance does not cover enterotoxigenic Escherichia coli, a common travel-associated infection, this information about other key enteric pathogens can be used by travelers and clinicians in pre- and posttravel consultations.

Impacts of Culture-Independent Diagnostic Practices on Public Health Surveillance for Bacterial Enteric Pathogens

For decades, culture has been the mainstay of diagnostic testing for bacterial enteric pathogens. This paradigm is changing as clinical laboratories adopt culture-independent methods, such as antigen-based tests and nucleic acid-based assays. Public health surveillance for enteric infections addresses 4 interrelated but distinct objectives: case investigation for localized disease control; assessment of disease burden and trends to prioritize and assess impact of population-based control measures; outbreak detection; and microbiologic characterization to improve understanding of pathogens, their virulence mechanisms, and epidemiology. We summarize the challenges and opportunities that culture-independent tests present and suggest strategies, such as validation studies and development of culture-independent tests compatible with subtyping, that could be adopted to ensure that surveillance remains robust. Many of these approaches will require time and resources to implement, but they will be necessary to maintain a strong surveillance system. Public health practitioners must clearly explain the value of surveillance, especially how outbreak detection benefits the public, and collaborate with all stakeholders to develop solutions.