Contagious acute gastrointestinal infections

A novel RT-multiplex PCR for detection of Aichi virus, human parechovirus, enteroviruses, and human bocavirus among infants and children with acute gastroenteritis

A novel reverse transcription-multiplex polymerase chain reaction assay was developed to detect Aichi virus, human parechovirus, enteroviruses, and human bocavirus. A mixture of four pairs of published specific primers, 6261 and 6779, ev22(+) and ev22(-), F1 and R1, 188F and 542R, was used to amplify the viral genomes and specifically generate four different amplicon sizes of 519, 270, 440, and 354 bp for Aichi virus, human parechovirus, enteroviruses, and human bocavirus, respectively. A total of 247 fecal specimens previously screened for rotavirus, adenovirus, norovirus, sapovirus, and astrovirus-negative, collected from infants and children with acute gastroenteritis in Japan from July 2007 to June 2008, were tested further for the presence of the four viruses, Aichi virus, human parechovirus, enteroviruses, and human bocavirus, by RT-multiplex PCR. The total detection rate of these viruses was 26.7% (66 out of 247 samples). Of these, HPeV, EVs, and HBoV were identified in 20, 41, and 5 specimens. No Aichi virus was found among these subjects. The sensitivity and specificity of RT-multiplex PCR were assessed and demonstrated a strong validation against RT-monoplex PCR. This is the first report of detecting these types of viruses in fecal samples from infants and children with acute gastroenteritis by RT-multiplex PCR.

Prevention and treatment of viral diarrhea in pediatrics

Diarrhea is the second largest cause of mortality worldwide in children from the perinatal period to the age of 5 years. Rotavirus has been the most commonly identified viral cause of diarrhea in children. Norovirus is now recognized as the second most common viral pathogen. Adenovirus, astrovirus and sapovirus are the other major viral causes of pediatric gastroenteritis. Strategies for prevention include basic hygiene, optimization of nutrition and, ultimately, vaccination. Two new vaccines have recently been licensed for the prevention of rotavirus, the monovalent human rotavirus vaccine (Rotarix) and the pentavalent bovine-human reassortant vaccine (RotaTeq). These vaccines have already dramatically decreased the morbidity associated with rotavirus in countries where they are widely used. Efforts to develop a norovirus vaccine face substantial hurdles. Treatment of the viral pathogens is primarily limited to symptomatic measures.

Norovirus disease associated with excess mortality and use of statins: a retrospective cohort study of an outbreak following a pilgrimage to Lourdes

Although norovirus infection is generally known to be a mild disease, there is some evidence for severe outcome. An outbreak in a Dutch psychiatric institution, originating from pilgrims returning from Lourdes (France), provided an opportunity for performing a retrospective cohort study in order to identify risk factors for norovirus disease and excess mortality. Relative risks (RR) including 95% confidence intervals (CI) showed that attending the pilgrimage (RR 2·0, 95% CI 1·4–3·0) and age >70 (RR 1·7, 95% CI 1·2–2·2) were risk factors for symptomatic infection. In a subset of patients, for whom more detailed information was available, the use of statins was associated with norovirus disease when adjusted for underlying condition (adjusted odds ratio 3·9, 95% CI 1·2–13·0). Mortality was higher in cases infected during the pilgrimage compared to other residents (RR 20·9, 95% CI 4·7–93·8). Norovirus disease can lead to severe outcome. The newly identified risk of statins for contracting norovirus disease may have considerable consequences for the Western world and needs prospective confirmation.

Norovirus gastroenteritis

Recent epidemiologic studies have shown that norovirus is one of the most frequent causes of acute nonbacterial gastroenteritis. Reverse-transcription polymerase chain reaction and nucleotide sequencing are the means by which the hundreds of norovirus strains have been identified, named, and classified into genogroups and genetic clusters. They are also the means by which a particular strain is traced from the source of an outbreak throughout its spread. These molecular techniques have been combined with classic epidemiology to investigate norovirus outbreaks in diverse settings, including hospitals, nursing homes, dining locations, schools, daycare centers, and vacation venues. Outbreaks are difficult to control because of the apparent ease of transmission through food, water, person-to-person contact, and environmental surfaces. Almost all patients with norovirus gastroenteritis recover completely, but hospital and nursing home outbreaks have been associated with morbidity and mortality. The diagnostic and management approach to an individual patient is to use clinical and epidemiologic findings to rule out "not norovirus." At the first sign that there is an outbreak, strict compliance with cleaning, disinfection, and work release guidelines is important to prevent further spread.

Pepper mild mottle virus, a plant virus associated with specific immune responses, Fever, abdominal pains, and pruritus in humans

BACKGROUND

Recently, metagenomic studies have identified viable Pepper mild mottle virus (PMMoV), a plant virus, in the stool of healthy subjects. However, its source and role as pathogen have not been determined.

METHODS AND FINDINGS

21 commercialized food products containing peppers, 357 stool samples from 304 adults and 208 stool samples from 137 children were tested for PMMoV using real-time PCR, sequencing, and electron microscopy. Anti-PMMoV IgM antibody testing was concurrently performed. A case-control study tested the association of biological and clinical symptoms with the presence of PMMoV in the stool. Twelve (57%) food products were positive for PMMoV RNA sequencing. Stool samples from twenty-two (7.2%) adults and one child (0.7%) were positive for PMMoV by real-time PCR. Positive cases were significantly more likely to have been sampled in Dermatology Units (p<10(-6)), to be seropositive for anti-PMMoV IgM antibodies (p = 0.026) and to be patients who exhibited fever, abdominal pains, and pruritus (p = 0.045, 0.038 and 0.046, respectively).

CONCLUSIONS

Our study identified a local source of PMMoV and linked the presence of PMMoV RNA in stool with a specific immune response and clinical symptoms. Although clinical symptoms may be imputable to another cofactor, including spicy food, our data suggest the possibility of a direct or indirect pathogenic role of plant viruses in humans.

Infectious diarrhea: Cellular and molecular mechanisms

Diarrhea caused by enteric infections is a major factor in morbidity and mortality worldwide. An estimated 2-4 billion episodes of infectious diarrhea occur each year and are especially prevalent in infants. This review highlights the cellular and molecular mechanisms underlying diarrhea associated with the three classes of infectious agents, i.e., bacteria, viruses and parasites. Several bacterial pathogens have been chosen as model organisms, including Vibrio cholerae as a classical example of secretory diarrhea, Clostridium difficile and Shigella species as agents of inflammatory diarrhea and selected strains of pathogenic Escherichia coli (E. coli) to discuss the recent advances in alteration of epithelial ion absorption. Many of the recent studies addressing epithelial ion transport and barrier function have been carried out using viruses and parasites. Here, we focus on the rapidly developing field of viral diarrhea including rotavirus, norovirus and astrovirus infections. Finally we discuss Giardia lamblia and Entamoeba histolytica as examples of parasitic diarrhea. Parasites have a greater complexity than the other pathogens and are capable of creating molecules similar to those produced by the host, such as serotonin and PGE(2). The underlying mechanisms of infectious diarrhea discussed include alterations in ion transport and tight junctions as well as the virulence factors, which alter these processes either through direct effects or indirectly through inflammation and neurotransmitters.

Is environmental tobacco smoke exposure a risk factor for acute gastroenteritis in young children?

Because passive smoke exposure has not been previously linked to diarrhea diseases in children, it was hypothesized that very young children exposed to environmental tobacco smoke (ETS) exposure at home would also be more likely to develop infectious gastroenteritis (GE) than their unexposed counterparts. During 1-year period, 260 children 36 months and younger were prospectively followed up in a private pediatric practice in a southern community in the United States. Multiple logistic regression analysis showed that ETS was strongly predictive of acute GE in the univariate analysis (P = .003). Even after controlling for the various confounders, ETS exposure was still significantly associated with acute GE (relative risk = 2.55; 95% CI = 1.26-5.18). It is speculated that, similar to acute respiratory infections, the same mechanisms may explain why ETS may also be associated with acute infectious GE.

Nosocomial and antibiotic-associated diarrhoea caused by organisms other than Clostridium difficile

Most cases of nosocomial and antibiotic-associated diarrhoea are caused by alteration of the physiological gut microflora. This alteration leads to reduced microbial metabolism of carbohydrates and primary bile acids, resulting in osmotic or secretory forms of diarrhoea. Moreover, facultative enteropathogens may experience a growth advantage due to the antibiotic-induced microflora alteration that, in turn, can harm the gut mucosa by the toxins they produce. Clostridium difficile is the major infectious agent leading to pseudomembranous colitis. However, there is increasing evidence that certain other pathogens such as enterotoxin-producing Clostridium perfringens, Staphylococcus aureus and Klebsiella oxytoca can induce mucosal deterioration and diarrhoea after antibiotic use. But, as with C. difficile, these facultative enteropathogens can also be found in the healthy population. Their contribution to disease is, therefore, controversial and their presence in the stools of antibiotic-associated diarrhoea patients is often claimed to be mere colonisation. In this respect, the causal relationship of each suspected pathogen with the development of intestinal disease has to be proved clinically and experimentally.

Immunity to Campylobacter: its role in risk assessment and epidemiology

Acquired immunity is an important factor in the epidemiology of campylobacteriosis in the developing world, apparently limiting symptomatic infection to children of less than two years. However, also in developed countries the highest incidence is observed in children under five years and the majority of Campylobacter infections are asymptomatic, which may be related to the effects of immunity and/or the ingested doses. Not accounting for immunity in epidemiological studies may lead to biased results due to the misclassification of Campylobacter-exposed but apparently healthy persons as unexposed. In risk assessment studies, health risks may be overestimated when immunity is neglected.

Focus on acute diarrhoeal disease

Diarrhoea is an alteration of normal bowel movement characterized by an increase in the water content, volume, or frequency of stools. Diarrhoea needs to be classified according to the trends over time (acute or chronic) and to the characteristics of the stools (watery, fatty, inflammatory). Secretory diarrhoeas, mostly acute and of viral aetiology in more than 70% of cases, are by far the most important subtype of diarrhoeas in terms of frequency, incidence and mortality (over 2.5 million deaths/year in developing countries). Natural and synthetic opiates such as morphine, codeine, and loperamide which react with endogenous opiates (enkephalins, beta-endorphins, dynorphins) mainly act on intestinal motility and slow down transit. An antidiarrhoeal drug developed in recent years, racecadotril, acts as an enkephalinase inhibitor. Clinical studies have shown that it is just as effective as loperamide in resolving acute diarrhoea but with greater reduction in pain and abdominal distension. Some studies have explored the prevalence of diarrhoea in old age. An epidemiological study carried out in Italy by 133 General Practitioners on 5515 elderly outpatients reported a prevalence of diarrhoea, defined according to the Rome criteria, of 9.1%. Infectious diseases (19%) and drug use (16%) were the most common causes of diarrhoea in old age. Regardless of the cause, the treatment of elderly patients with diarrhoea must include rehydration and nutritional support. Every year, more than 50 million tourists travel from industrialized countries to places where hygiene levels are poor. At least 75% of those travelling for short periods mention health problems, and in particular traveller’s diarrhoea.

[Diarrhea from the infectologist's point of view]

Gastroenteritis is a nonspecific term for various pathologic states of the gastrointestinal tract. Gastroenteritis causing pathogens are the second leading cause of morbidity and mortality worldwide. In the developed countries diarrhea is the most common reason for missing work, while in the developing world, it is a leading cause of death. Internationally, the mortality rate is 5-10 million deaths each year. "Traveller's diarrhea" is a polyetiologic common health problem of international travellers which affects travellers generally for days, but it can result in chronic postinfectious irritable bowel syndrome as well. Infectious agents usually cause acute gastroenteritis either by adherence of the intestinal mucosa, or by mucosal invasion, enterotoxin production, and/or cytotoxin production. The incubation period can often suggest the cause of etiology. When symptoms occur within 6 hours of eating, ingestion of preformed toxin of S. aureus or Bacillus cereus should be suspected. The incidence of hypervirulent C. difficile associated colitis is an emerging problem as a healthcare system associated infection. While infectious agents do not commonly cause chronic diarrhea, those that do include C. difficile, Giardia lamblia, Entamoeba histolytica, Cryptosporidium, Aeromonas and Yersinia . Amoebiasis is the second to malaria as a protozoal cause of death. Infection with HIV is also a common cause of diarrhea.

Rotavirus disease and prevention through vaccination

Rotavirus is the most common cause of acute infectious gastroenteritis in children and is associated with substantial morbidity in the United States and morbidity and mortality in the developing world. Two orally administered vaccines, a live bovine reassortant vaccine (RV5; licensed in 2006) and a live attenuated human vaccine (RV1; licensed in 2008), are now being used in a universal infant vaccination program in the United States. There is already ecologic evidence and data from post-licensure effectiveness studies that this program will be an unequivocal success in reducing the impact of rotavirus disease. This overview presents the structure, pathogenesis, and mechanisms of natural immunity to rotavirus, key concepts in understanding the rationale behind vaccine-induced protection. The history of rotavirus vaccine development is also included, along with a discussion of the safety, efficacy, and recommended use of the approved vaccines.

The changing panorama of bacterial enteric infections

We studied the age-specific population-based incidence of bacterial enteric infections caused by Shigella, Salmonella and Campylobacter, in Jerusalem. During 1990–2008, 32 408 cases were reported (incidence rate 232·1/100 000 per annum). The patterns of Shigella (47·4% of cases), Salmonella (34·4%) and Campylobacter (18·2%) infections evolved noticeably. Campylobacter rates increased from 15·0 to 110·8/100 000 per annum. Salmonella rates increased from 74·2 to 199·6/100 000 in 1995 then decreased to 39·4/100 000. Shigella showed an endemic/epidemic pattern ranging between 19·7 and 252·8/100 000. Most patients (75%) were aged <15 years; children aged <5 years comprised 56·4% of cases, despite accounting for only 12·9% of the population. Campylobacter was the predominant organism in infants aged <1 year and Shigella in the 1–4 years group. The hospitalization rates were: Shigella, 1·8%; Campylobacter, 2·3%; Salmonella, 6·9%. Infants were 2·2 times more likely to be hospitalized than children aged 1–14 years (P=0·001). Household transmission occurred in 21·2% of Shigella cases compared with 5% in the other bacteria.

Association between indicators of livestock farming intensity and hospitalization rate for acute gastroenteritis

To evaluate associations between indicators of livestock farming intensity (manure surplus and livestock density) and acute gastroenteritis hospitalization (AGH) rate, we conducted an ecological study on 306 selected agricultural municipalities of Quebec. We estimated the AGH rate for the period 2000–2004 from the Quebec hospital database. Multivariate Poisson regression was used to estimate the strength of association between the farming indicators and AGH with adjustment for confounders. The modifying effect of age and water source was also evaluated. Association between manure and AGH was observed in children, especially those aged 0–4 years for selected zoonotic infections [adjusted hospitalization rate ratio (aHRR) 1·93, 95% CI 1·21–3·09]. The risk ratio was higher for subjects using ground-water source. An increasing HRR trend with each additional level of poultry density was observed in children aged 0–4 years, especially forSalmonellainfections. We conclude that livestock farming intensity may be linked to bacterial acute gastroenteritis in children.

Outbreaks where food workers have been implicated in the spread of foodborne disease. Part 4. Infective doses and pathogen carriage

In this article, the fourth in a series reviewing the role of food workers in foodborne outbreaks, background information on the presence of enteric pathogens in the community, the numbers of organisms required to initiate an infection, and the length of carriage are presented. Although workers have been implicated in outbreaks, they were not always aware of their infections, either because they were in the prodromic phase before symptoms began or because they were asymptomatic carriers. Pathogens of fecal, nose or throat, and skin origin are most likely to be transmitted by the hands, highlighting the need for effective hand hygiene and other barriers to pathogen contamination, such as no bare hand contact with ready-to-eat food. The pathogens most likely to be transmitted by food workers are norovirus, hepatitis A virus, Salmonella, Shigella, and Staphylococcus aureus. However, other pathogens have been implicated in worker-associated outbreaks or have the potential to be implicated. In this study, the likelihood of pathogen involvement in foodborne outbreaks where infected workers have been implicated was examined, based on infectious dose, carriage rate in the community, duration of illness, and length of pathogen excretion. Infectious dose estimates are based on volunteer studies (mostly early experiments) or data from outbreaks. Although there is considerable uncertainty associated with these data, some pathogens appear to be able to infect at doses as low as 1 to 100 units, including viruses, parasites, and some bacteria. Lengthy postsymptomatic shedding periods and excretion by asymptomatic individuals of many enteric pathogens is an important issue for the hygienic management of food workers.

Aetiology of community-acquired, acute gastroenteritis in hospitalised adults: a prospective cohort study

Background

The aetiology of severe gastroenteritis leading to hospitalisation in adults frequently remains unclear. Our objective was to study the causes and characteristics of community-acquired, acute gastroenteritis in adult hospitalized patients to support the clinical management of these patients.

Methods

From August 2005 to August 2007, we conducted a prospective cohort study among patients ≥18 y hospitalized with community-acquired gastroenteritis in a university hospital in Berlin, Germany. Stool specimens were examined for 26 gastrointestinal pathogens, supplemented by serologic tests for antibodies to Campylobacter spp., Yersinia spp., and Entamoeba histolytica. Patient data on demographics and clinical presentation were recorded and analyzed. Coexisting medical conditions were assessed using the Charlson Comorbidity Index score.

Results

Of 132 patients presenting with acute community-acquired gastroenteritis, 104 were included in the study. A non-infectious aetiology was diagnosed in 8 patients (8%). In 79 (82%) of the remaining 96 patients at least one microorganism was identified. Campylobacter spp. (35%) was detected most frequently, followed by norovirus (23%), Salmonella spp. (20%), and rotavirus (15%). In 46% of the patients with Campylobacter spp. infection, the diagnosis was made solely by serology. More than one pathogen was found in seventeen (22%) patients. Simultaneous infection was significantly more likely in patients with rotavirus and salmonella infections (RR 3.6; 95% CI: 1.8–7.4; RR 2.5; 95%CI: 1.2–5.5). Length of hospital stay (median: 5.5 days) was independent of the pathogen, but was associated with coexisting medical conditions (OR 4,8; 95%CI:2,0–11,6).

Conclusion

Known enteric pathogens were detected in 82% of adult patients who were hospitalized with acute gastroenteritis. We found that currently used culture-based methods may miss a substantial proportion of Campylobacter infections, and additional serological testing for Campylobacter should be considered. Viral infections emerged as an important cause of severe gastroenteritis in adults, and viral-bacterial co-infections in adults are probably underrecognized so far. The presence of coexisting medical conditions – but not the etiological agent – was a predictor for the duration of the hospital stay.

Mechanisms of infectious diarrhea

Infectious diarrhea is an important public health problem worldwide. Research has provided new insights into the mechanisms of diarrhea caused by various pathogens that are classified as noninflammatory, inflammatory or invasive. These three groups of organisms cause two diarrheal syndromes--noninflammatory diarrhea and inflammatory diarrhea. The noninflammatory diarrheas are caused by enterotoxin-producing organisms such as Vibrio cholerae and enterotoxigenic Escherichia coli, or by viruses that adhere to the mucosa and disrupt the absorptive and/or secretory processes of the enterocyte without causing acute inflammation or mucosal destruction. Inflammatory diarrhea is caused by two groups of organisms--cytotoxin-producing, noninvasive bacteria (e.g. enteroaggregative Escherichia coli, enterohemorrhagic Escherichia coli and Clostridium difficile), or by invasive organisms (e.g. Salmonella spp., Shigella spp., Campylobacter spp., Entamoeba histolytica). The cytotoxin-producing organisms adhere to the mucosa, activate cytokines and stimulate the intestinal mucosa to release inflammatory mediators. Invasive organisms, which can also produce cytotoxins, invade the intestinal mucosa to induce an acute inflammatory reaction, involving the activation of cytokines and inflammatory mediators. Regardless of the underlying mechanism they use, these various types of pathogen have all successfully evolved to evade and modulate the host defense systems. The mechanisms by which the different pathogens invade the host and cause infectious diarrhea are the topic of this Review.

Stool cultures and antimicrobial prescriptions related to infectious diarrhea

Stool cultures can be important in guiding antimicrobial therapy for diarrhea. From among 11.64 million person-years of Tennessee Medicaid enrollment data collected from 1995 through 2004, 315,828 diarrheal episodes were identified. Stool cultures were performed for only 15,820 episodes (5.0%). Antimicrobials were prescribed for 32,949 episodes (10.4%), 89.4% of which were not accompanied by a stool culture. White race and urban residence were associated with higher rates of stool culture. Frequent use of antimicrobials for diarrhea without stool culture may indicate inappropriate antimicrobial use and has critical implications for public health.

Foodborne illness

While few patients with foodborne illness present with life-threatening symptoms, there are a number of foodborne infectious diseases and toxins that the emergency physician or other health care provider must consider in the evaluation of these patients. Given the frequency of international travel, as well as the risk associated with recurrent outbreaks of foodborne illness from commercial food sources, it is important to recognize various syndromes of foodborne illness, including those which may require specific evaluation and management strategies. This article reviews a number of the most common causes of foodborne illness, as well as several less common pathogens with the potential for causing significant morbidity and mortality if not promptly identified and treated.

Certainties and uncertainties facing emerging respiratory infectious diseases: lessons from SARS

Every emerging infectious disease is a challenge to the whole of mankind. There are uncertainties regarding whether there will be a pandemic, if it will be caused by the highly pathogenic H5N1 influenza virus, when or where it will occur, how imminent or how severe it will be. No one can accurately predict if and when a given virus will become a pandemic virus. Pandemic prevention strategies must be based on preparing for the unexpected and being capable of reacting accordingly. There is growing evidence that infection control measures were helpful in containment of severe acute respiratory syndrome (SARS) as well as avian influenza. Compliance of standard infection control measures, intensive promotion of hand and respiratory hygiene, vigilance and triage of patients with febrile illness, and specific infection control measures are key components to contain a highly contagious disease in hospital and to protect healthcare workers, patients and visitors. The importance of standard precautions for any patient and cleaning and disinfection for the healthcare environment cannot be overemphasized. SARS illustrated dramatically the potential of air travel and globalization for the dissemination of an emerging infectious disease. To prevent the potential serious consequences of pandemic influenza, timely implementation of pharmaceutical and non-pharmaceutical interventions locally within the outbreak area is the key to minimizing global spread. Herein, we relate our perspective on useful lessons derived from a review of the SARS epidemic that may be useful to physicians, especially when looking ahead to the next epidemic.

Diarrheal diseases in the elderly

Diarrhea in the elderly population is one disease that needs special attention in treatment and management, especially in acute- and long-term care residents, because of their multiple comorbidities, immunosenescence, frailty, and poor nutritional status. Close follow-up to ensure adequate hydration and electrolyte replacement and infection control measures to contain outbreaks should be emphasized to caregivers and nursing staff in acute- and long-term care facilities. Although C difficile colitis causes significant morbidity and mortality in this population, judicious use of antibiotics is important to decrease the incidence and recurrence of the disease. When the diarrhea is chronic and all stool testings and serologies have been performed, the patient may benefit from endoscopy and colonoscopy for biopsy. Attentive and vigilant nursing staff is crucial in the timely diagnosis and treatment of diarrheal diseases to improve quality of life and reduce mortality.

[Infectious aetiologies of travelers' diarrhoea]

Traveler's diarrhoea (TD) occurs in 20 to 60% of European or North-American travelers in intertropical areas. Following return from endemic zone, malaria must always be evocated in front of febrile diarrhoea. Many causative infectious agents are involved in TD and their frequency may vary according to destination and seasons. The main agents involved in TD are Escherichia coli pathovars (especially enterotoxigenic and enteroaggregative E. coli) followed by enteroinvasive bacteria (Campylobacter spp., Shigella spp., Salmonella enterica), enteric viruses (norovirus, rotavirus) and protozoa (Gardia intestinalis, Cryptosporidium parvum et Entamoeba histolytica). The development of molecular biology methods as PCR may allow us to evaluate the relative frequency of these agents and especially of viral agents in TD. Protozoa and microsporidia are more frequently isolated in persistent and chronic TD, especially in compromised patients. A complete etiological research in routine microbiology laboratories is difficult and time-consuming, related to the high diversity of causative agents and the need for specific methods. Implementation of laboratory diagnosis is highly recommended when diarrhoea is associated with fever or presence of blood in stools, immunosuppression, antibiotic treatment (Clostridium difficile toxins) or in case of persistent/chronic diarrhoea. According to the high frequency of acquired antibiotic-resistance in enteric bacteria, an antibiogram must be performed for all causative bacterial agents.

Internationally Distributed Frozen Oyster Meat Causing Multiple Outbreaks of Norovirus Infection in Australia

BACKGROUND

Between November 2003 and January 2004, outbreaks of norovirus in 3 Australian jurisdictions involving 83 cases of illness were associated with imported oyster meat.

METHODS

Cohort studies were conducted in 2 jurisdictions to identify relative risks of illness for the consumption of oysters. A case series was conducted in the third jurisdiction.

RESULTS

The cohort studies conducted in the first 2 jurisdictions identified relative risks of illness of 17 (95% confidence interval, 5-51) and 35 (95% confidence interval, 5-243), respectively, for the consumption of oysters. Multiple strains of norovirus were detected in fecal specimens from 8 of 14 patients and in 1 of the 3 batches of implicated oyster meat using seminested reverse-transcriptase polymerase chain reaction methods. Traceback investigations revealed that all oyster meat was harvested from the same estuary system in Japan within the same month.

CONCLUSIONS

These outbreaks demonstrate the potential of foodborne disease to spread internationally and the need for national and international collaboration to investigate such outbreaks. Foodborne illness related to norovirus is underestimated because of underreporting of human cases and challenges in laboratory detection of viruses in foods, both of which can delay public health action.

Parasitic colitides

Parasitic infections are a major worldwide health problem, and they account for millions of infections and deaths each year. Most of the infections as well as the morbidity and mortality from these diseases occur in the developing world in rural regions. However, these diseases have become more common in Western countries and in big cities over the past 25 years. These changing disease patterns can be attributed to emigration from the third world to developed countries and migration of rural populations to the big cities in developing nations. These parasitic infections have protean manifestations and consequences. The medical problems range from chronic asymptomatic carrier to fulminant infections and even death. Several factors such as the host immune status, the infecting organism, and the availability of treatment all play key roles in the outcomes of parasitic colitides. The two major classes of parasites causing these infections are the helminthes (ascariasis, strongyloidiasis, enterobiasis, trichuriasis, and schistosomiasis) and the protozoa (Isospora, Cryptosporidium, Cyclospora, Trypanosoma cruzi, Giardia lamblia, and Balantidium coli). This article summarizes the salient features of each parasite with respect to epidemiology, transmission, pathogenesis, clinical features, diagnosis, and treatment. The vast majority of these infections have a self-limited clinical course or are easily treated with medical management, and surgery is rarely needed.

Diarrhea in nontravelers: risk and etiology

Acute diarrheal illnesses in nontravelers are common and represent a significant health and economic burden in the United States and other developed countries. The likelihood of experiencing diarrhea is increased many fold during travel to developing countries. Extensive overlap exists in the pathogens that cause diarrhea in travelers and nontravelers, although proportions differ and show variation by geographic area and by season, and they change over time. Rates of infection are highest in infants and young children, in whom viral pathogens predominate. Person-to-person transmission may account for more than one-half of cases. In contrast, in many studies, bacterial infections predominate in travelers, who often acquire infection from contaminated food and water. Because of the globalization of the food supply, clinicians in developed countries should expect to continue to see sporadic cases and outbreaks of diarrhea caused by unusual pathogens, such as Cyclospora species.

Norovirus gastroenteritis

Recent epidemiologic studies have shown that norovirus is one of the most frequent causes of acute nonbacterial gastroenteritis. Reverse-transcription polymerase chain reaction and nucleotide sequencing are the means by which the hundreds of norovirus strains have been identified, named, and classified into genogroups and genetic clusters. They are also the means by which a particular strain is traced from the source of an outbreak throughout its spread. These molecular techniques have been combined with classic epidemiology to investigate norovirus outbreaks in diverse settings, including hospitals, nursing homes, dining locations, schools, daycare centers, and vacation venues. Outbreaks are difficult to control because of the apparent ease of transmission through food, water, person-to-person contact, and environmental surfaces. Almost all patients with norovirus gastroenteritis recover completely, but hospital and nursing home outbreaks have been associated with morbidity and mortality. The diagnostic and management approach to an individual patient is to use clinical and epidemiologic findings to rule out "not norovirus." At the first sign that there is an outbreak, strict compliance with cleaning, disinfection, and work release guidelines is important to prevent further spread.

Salmonella outbreaks in restaurants in Minnesota, 1995 through 2003: evaluation of the role of infected foodworkers

The 23 restaurant-associated salmonellosis outbreaks that occurred in Minnesota from 1995 through 2003 were reviewed to characterize the role of infected foodworkers. The median duration of the outbreaks was 21 days (range, 1 to 517 days). The median number of culture-confirmed patron cases per outbreak was seven (range, 1 to 36 cases). The median incubation for patron cases ranged from 9 h to 5.9 days. A specific food vehicle was implicated in four outbreaks and suspected in five. Salmonella of the same serotype and pulsed-field gel electrophoresis subtype as that found in patrons was recovered from foodworkers in 19 outbreaks. Overall, 12% (129 of 1,033) of foodworkers tested positive for Salmonella. Sixty-four (53%) of 121 Salmonella-positive foodworkers reported not having had a recent gastrointestinal illness. Overall, the median duration of Salmonella shedding was 16 days. Among foodworkers who reported gastrointestinal illness, the median shedding duration was 30 days as compared with 3 days for asymptomatic foodworkers. Positive environmental samples were recovered in 4 (33%) of 12 outbreaks. No specific food vehicle was identified in any outbreaks associated with Salmonella-positive environmental samples. The median duration of outbreaks with positive environmental samples (187 days) was significantly longer than the median duration of outbreaks with negative environmental results (26 days, P = 0.03). A higher proportion of Salmonella-positive foodworkers (22 versus 8%) was identified in outbreaks with positive environmental samples. Salmonella outbreaks in restaurants are frequently prolonged yet produce a small number of confirmed patron cases. Prolonged outbreak durations suggest a persistent reservoir of contamination. Infected foodworkers likely serve as an important source for Salmonella transmission. Therefore, assessment of foodworker infection is essential for controlling restaurant outbreaks.

A Bayesian approach to acute infectious diarrhea in adults

Acute infectious diarrhea is a yearly occurrence for most Americans, and is associated with 1 million hospitalizations and about 6000 deaths in the United States annually. Up to 80% of acute infectious diarrhea is caused by noroviruses, which produce a clinically mild illness with a predictable short course and good outcome that make laboratory testing and antimicrobial treatment unnecessary. Most diarrhea-causing bacteria and protozoa can cause a clinical illness "like norovirus"; when they do so in healthy adults neither specialized testing nor antimicrobials is required. The presence or absence of epidemiologic evidence (such as travel, hospitalization, antibiotic use, other exposures)and clinical evidence (such as diarrhea frequency and duration, severity of abdominal pain and fever, character of stool, presence of chronic illness or immune deficiency) can change the probability of "not norovirus" from as low as 8% to as high as 100%. Such probabilities guide the use of laboratory testing and antimicrobial therapy in patients who have acute infectious diarrhea.

Laboratory-acquired infections: Are microbiologists at risk?

Exposure of laboratory workers to infectious agents in the clinical microbiology laboratory continues to be an occupational risk. This risk is mitigated by the application of safety guidelines issued by regulatory agencies and professional organizations. The Clinical and Laboratory Standards Institute (fomerly NCCLS) published a guidance document (M29-A3) in 2005 on the risk of transmission of infectious agents in the laboratory, preventative measures to reduce risk, and management of exposure to infectious agents. The key to a safe workplace is employees who are knowledgeable of the routes of transmission of infectious agents in the laboratory setting and apply safety principles and work practices to reduce the risk.

Training room management of medical conditions: infectious diseases

Management of infectious diseases in athletes encompasses a wide range of pathogens, clinical presentations, and treatment options. Certain athletic activities and training regimens may predispose athletes to increased risk of contracting infectious diseases, some of which may limit athletic participation and pose the threat of significant morbidity. The sports medicine physician plays an important role as a first line of defense in preventing, recognizing, and appropriately treating infectious diseases in athletes.