Shuyu Wu

Laboratory-Based Surveillance of Nontyphoidal Salmonella Infections in China

Foodborne infections are an important public health problem in China. In 2008, we conducted surveillance for laboratory-confirmed nontyphoidal Salmonella to monitor trends for this infection in China and to build capacity for rapid detection and response to foodborne outbreaks. Salmonella isolates from patients with diarrhea were sent from hospitals to local public health laboratories for confirmation, serotyping, and antimicrobial susceptibility testing. A total of 126 hospitals in 44 cities and counties from 8 provinces provided isolates and epidemiologic data for analysis. Of 23,140 stool specimens submitted to clinical laboratories, 662 (3%) grew Salmonella enterica. Salmonella were most commonly detected between April and October. The median age of infected patients was 27 years; 34% of infections occurred in patients <5 years old. Of the 662 isolates, we found 73 serotypes, of which serotype Enteritidis (31%) and serotype Typhimurium (26%) were the most common. The prevalence of resistance was high for clinically important antimicrobial agents, including ampicillin (41%) and ciprofloxacin (6%). More than 60% of isolates, including 35% of all Typhimurium, were resistant to three or more antimicrobial agents. In this first multiprovince surveillance report of laboratory-confirmed Salmonella infections in China, we found that Enteritidis and Typhimurium are the most common serotypes and that efforts to reduce antimicrobial resistance among Salmonella in China are needed. Although no outbreaks were detected using this system, efforts to improve this systems capacity to do so are underway.

Laboratory-Based Surveillance of Non-typhoidal Salmonella Infections in Guangdong Province, China

Salmonella is one of the most common foodborne pathogens in humans. Laboratory-based surveillance for non-typhoidal Salmonella infection was conducted in Guangdong Province, China to improve understanding about the disease burden and detection of dispersed outbreaks. Salmonella isolated from patients with diarrhea were sent from 16 sentinel hospitals to local public health laboratories for confirmation, serotyping, antimicrobial susceptibility testing, and pulsed-field gel electrophoresis (PFGE). PFGE patterns were analyzed to identify clusters representing potential outbreaks. Between September 2009 and October 2010, 352 (4%) Salmonella isolates were obtained from 9167 stool specimens. Salmonella enterica serotype Typhimurium (45%) and Salmonella enterica serotype Enteritidis (13%) were the most common serotypes, and multidrug resistance was high, especially in Salmonella Typhimurium isolates. PFGE patterns of obtained Salmonella isolates were found to be diverse, but a unique PFGE pattern comprising 53 Salmonella Typhimurium isolates were found to occur almost exclusively in infants. Epidemiologic studies are ongoing to determine whether a common exposure is the source of the Salmonella Typhimurium strain frequently isolated from infants.

Epidemiological and Etiological Characteristics of Hand, Foot, and Mouth Disease in Henan, China, 2008–2013

Hand, foot, and mouth disease (HFMD) is a common childhood illness caused by enteroviruses. HFMD outbreaks and reported cases have sharply increased in China since 2008. Epidemiological and clinical data of HFMD cases reported in Henan Province were collected from 2008 to 2013. Clinical specimens were obtained from a subset of these cases. Descriptive epidemiological methods were used to analyze the time, region and population distribution. The VP1 gene from EV71 and CA16 isolates was amplified, and the sequences were analyzed. 400,264 cases of HFMD were reported in this study, including 22,309 severe and 141 fatal cases. Incidence peaked between April and May. Laboratory confirmation was obtained for 27,692 (6.9%) cases; EV71, CA16, and other enteroviruses accounted for 59.5%, 14.1%, 26.4%, respectively. Phylogenetic analysis revealed that EV71 belonged to the C4a evolution branch of C4 sub-genotype and CA16 belonged to subtype B1a or B1b. The occurrence of HFMD in Henan was closely related to season, age and region distribution. Children under five were the most affected population. The major pathogens causing HFMD and their genotypes have not notably changed in Henan. The data strongly support the importance of EV71 vaccination in a high population density area such as Henan, China.

Risk Factors for Vibrio parahaemolyticus Infection in a Southern Coastal Region of China

OBJECTIVES The objectives of the study were to identify dietary and medical risk factors for Vibrio parahaemolyticus (VP) infection in the coastal city Shenzhen in China. METHODS In April-October 2012, we conducted a case-control study in two hospitals in Shenzhen, China. Laboratory-confirmed VP cases (N = 83) were matched on age, sex, and other social factors to healthy controls (N = 249). Subjects were interviewed using a questionnaire on medical history; contact with seawater; clinical symptoms and outcome; travel history over the past week; and dietary history 3 days prior to onset. Laboratory tests were used to culture, serotype, and genotype VP strains. We used logistic regression to calculate the odds ratios for the association of VP infection with potential risk factors. RESULTS In multivariate analysis, VP infection was associated with having pre-existing chronic disease (adjusted odds ratio [aOR], 6.0; 95% confidence interval [CI], 1.5-23.7), eating undercooked seafood (aOR, 8.0; 95% CI, 1.3-50.4), eating undercooked meat (aOR, 29.1; 95% CI, 3.0-278.2), eating food from a street food vendor (aOR, 7.6; 95% CI, 3.3-17.6), and eating vegetable salad (aOR, 12.1; 95% CI, 5.2-28.2). CONCLUSIONS Eating raw (undercooked) seafood and meat is an important source of VP infection among the study population. Cross-contamination of VP in other food (e.g., vegetables and undercooked meat) likely plays a more important role. Intervention should be taken to lower the risks of cross-contamination with undercooked seafood/meat, especially targeted at people with low income, transient workers, and people with medical risk factors.

Systematic review of human listeriosis in China, 1964-2010

Listeria is an important foodborne pathogen with severe manifestations and high case‐fatality rate. However, listeriosis is not yet a notifiable disease in China, and there is no national monitoring system for cases. We conducted a systematic review to better understand the clinical and epidemiologic features of listeriosis in China.

Survey of Physician Diagnostic and Treatment Practices for Patients with Acute Diarrhea in Guangdong Province, China

Although international clinical guidelines generally recommend performing bacterial stool culture in patients with acute diarrhea and fever and discourage routine antibiotic prescribing, clinical practice varies. Understanding practice patterns can help health officials assess the sensitivity of laboratory-based enteric infection surveillance systems and the need to improve antibiotic prescribing practices. We surveyed physicians in Guangdong province, China, to measure their practices for patients with acute diarrhea. A standardized questionnaire was used to interview physicians working in hospitals participating in a Salmonella surveillance system in Guangdong, China. The questionnaire asked physicians about their routine practice for patients with diarrhea, including how they managed the last patient they had seen with acute diarrhea. We calculated the odds ratio and 95% confidence interval for factors associated with ordering a stool culture and for prescribing antibiotics. We received surveys from 237 physicians across 22 hospitals in Guangdong. For the last patient with diarrhea whom they had evaluated, 134 (57%) reported ordering a stool culture. The most common reasons for not ordering a stool culture included that it takes too long to receive the result, that the patient is not willing to pay for the test, and that the patients illness was too mild to warrant testing. Most physicians prescribed at least one medication for the last patient with diarrhea whom they had evaluated. Of the 237 physicians surveyed, 153 (65%) prescribed antibiotics, 135 (57%) probiotics, and 115 (49%), a gastric mucosal protective drug. In conclusion, physicians in Guangdong, China, reported high rates of ordering bacterial stool cultures from patients with diarrhea, possibly associated with their hospitals participation in a special surveillance project. The high rate of antibiotic prescribing suggests that efforts to promote judicious antibiotic use, such as physician education, are needed.

A Large-Scale Community-Based Outbreak of Paratyphoid Fever Caused by Hospital-Derived Transmission in Southern China.

Background Since the 1990s, paratyphoid fever caused by Salmonella Paratyphi A has emerged in Southeast Asia and China. In 2010, a large-scale outbreak involving 601 cases of paratyphoid fever occurred in the whole of Yuanjiang county in China. Epidemiological and laboratory investigations were conducted to determine the etiology, source and transmission factors of the outbreak. Methodology/Principal Findings A case-control study was performed to identify the risk factors for this paratyphoid outbreak. Cases were identified as patients with blood culture–confirmed S. Paratyphi A infection. Controls were healthy persons without fever within the past month and matched to cases by age, gender and geography. Pulsed-field gel electrophoresis and whole-genome sequencing of the S. Paratyphi A strains isolated from patients and environmental sources were performed to facilitate transmission analysis and source tracking. We found that farmers and young adults were the populations mainly affected in this outbreak, and the consumption of raw vegetables was the main risk factor associated with paratyphoid fever. Molecular subtyping and genome sequencing of S. Paratyphi A isolates recovered from improperly disinfected hospital wastewater showed indistinguishable patterns matching most of the isolates from the cases. An investigation showed that hospital wastewater mixed with surface water was used for crop irrigation, promoting a cycle of contamination. After prohibition of the planting of vegetables in contaminated fields and the thorough disinfection of hospital wastewater, the outbreak subsided. Further analysis of the isolates indicated that the origin of the outbreak was most likely from patients outside Yuanjiang county. Conclusions This outbreak is an example of the combined effect of social behaviors, prevailing ecological conditions and improper disinfection of hospital wastewater on facilitating a sustained epidemic of paratyphoid fever. This study underscores the critical need for strict treatment measures of hospital wastewater and the maintenance of independent agricultural irrigation systems in rural areas.

A large outbreak of acute gastroenteritis caused by the human norovirus GII.17 strain at a university in Henan Province, China

BackgroundHuman noroviruses are a major cause of viral gastroenteritis and are the main etiological agents of acute gastroenteritis outbreaks. An increasing number of outbreaks and sporadic cases of norovirus have been reported in China in recent years. There was a large acute gastroenteritis outbreak at a university in Henan Province, China in the past five years. We want to identify the source, transmission routes of the outbreak by epidemiological investigation and laboratory testing in order to provide the effective control measures.MethodsThe clinical cases were investigated, and analysed by descriptive epidemiological methods according to factors such as time, department, grade and so on. Samples were collected from clinical cases, healthy persons, the environment, water, and food at the university. These samples were tested for potential bacteria and viruses. The samples that tested positive for norovirus were selected for whole genome sequencing and the sequences were then analysed.ResultsFrom 4 March to 3 April 2015, a total of 753 acute diarrhoea cases were reported at the university; the attack rate was 3.29%. The epidemic curve showed two peaks, with the main peak occurring between 10 and 20 March, accounting for 85.26% of reported cases. The rates of norovirus detection in samples from confirmed cases, people without symptoms, and environmental samples were 32.72%, 17.39%, and 9.17%, respectively. The phylogenetic analysis showed that the norovirus belonged to the genotype GII.17.ConclusionsThis is the largest and most severe outbreak caused by genotype GII.17 norovirus in recent years in China. The GII.17 viruses displayed high epidemic activity and have become a dominant strain in China since the winter of 2014, having replaced the previously dominant GII.4 Sydney 2012 strain.

Incidence of norovirus-associated diarrhea, Shanghai, China, 2012–2013

We conducted sentinel-based surveillance for norovirus in the Pudong area of Shanghai, China, during 2012–2013, by analyzing 5,324 community surveys, 408,024 medical records, and 771 laboratory-confirmed norovirus infections among 3,877 diarrhea cases. Our analysis indicated an outpatient incidence of 1.5/100 person-years and a community incidence of 8.9/100 person-years for norovirus-associated diarrhea.

Nontyphoidal Salmonella Infection, Guangdong Province, China, 2012.

We used active and passive surveillance to estimate nontyphoidal Salmonella (NTS) infection during 2012 in Guangdong Province, China. Under passive surveillance, for every reported NTS infection, an estimated 414.8 cases occurred annually. Under active surveillance, an estimated 35.8 cases occurred. Active surveillance provides remarkable advantages in incidence estimate.