A gastroenteritis outbreak due to norovirus associated with a Colorado hotel

Describing the system components of norovirus outbreaks is important in understanding how to prevent future outbreaks. Investigation of these components includes environmental, epidemiologic, and laboratory perspectives. This study describes how an investigation from these three perspectives was conducted and the significance of each component in understanding norovirus outbreaks. On May 23, 2000, members of a professional group attending two meetings at a local hotel in Englewood, Colorado, began to complain of gastrointestinal illness. Sixty-nine illnesses were reported among 133 attendees. Eight hotel employees also complained of illness. Staff from the Tri-County Health Department and the Centers for Disease Control and Prevention investigated the outbreak. Three stool specimens collected from ill attendees contained norovirus. While the epidemiologic component did not identify a specific vehicle of transmission, the environmental investigation revealed food-handling practices, food handler perceptions, and hotel policies that may have contributed to disease transmission.     

An outbreak of norovirus gastroenteritis associated with wedding cakes

We sought to determine the source of a norovirus outbreak among attendees of 46 weddings taking place during a single weekend. Norovirus-compatible illness was experienced by 332 (39%) of wedding guests surveyed; the outbreak affected up to 2700 persons. Illness was associated with eating wedding cake provided by a bakery common to the weddings (adjusted RR 4.5, P<0.001). A cake requiring direct hand contact during its preparation accounted for the majority of illness. At least two bakery employees experienced norovirus-compatible illness during the week preceding the weddings. Identical sequence types of norovirus were detected in stool specimens submitted by two wedding guests, a wedding hall employee, and one of the ill bakery employees. It is likely that one or more food workers at the bakery contaminated the wedding cakes through direct and indirect contact. These findings reinforce the necessity of proper food-handling practices and of policies that discourage food handlers from working while ill.     

Multi-pathogen waterborne disease outbreak associated with a dinner cruise on Lake Michigan

We report an outbreak associated with a dinner cruise on Lake Michigan. This took place on the same day as heavy rainfall, which resulted in 42·4 billion liters of rainwater and storm runoff containing highly diluted sewage being released into the lake. Of 72 cruise participants, 41 (57%) reported gastroenteritis. Stool specimens were positive for Shigella sonnei (n=3), Giardia (n=3), and Cryptosporidium (n=2). Ice consumption was associated with illness (risk ratio 2·2, P=0·011). S. sonnei was isolated from a swab obtained from the one of the boat's ice bins. Environmental inspection revealed conditions and equipment that could have contributed to lake water contaminating the hose used to load potable water onto the boat. Knowledge of water holding and distribution systems on boats, and of potential risks associated with flooding and the release of diluted sewage into large bodies of water, is crucial for public health guidance regarding recreational cruises.     

Multistate outbreak of norovirus gastroenteritis among attendees at a family reunion--Grant County, West Virginia, October 2006

On October 17, 2006, the West Virginia Department of Health and Human Resources (WVDHHR) was notified of an outbreak of acute gastroenteritis, characterized by vomiting and diarrhea, among attendees at a family reunion. The outbreak initially was reported by a group of attendees to their local health department in Garrett County, Maryland. The same day, the information was relayed to the Grant County Health Department in West Virginia and subsequently to WVDHHR. The reunion was held on October 14 at a private residence in Grant County, West Virginia, and the 53 identified attendees included residents from Florida, Maryland, New York, Pennsylvania, Virginia, and West Virginia. This report describes a collaborative, multijurisdictional epidemiologic investigation using a cohort study and laboratory analyses to determine the source of infection and appropriate control measures. The results indicated that a combination of person-to-person and foodborne transmission of two strains of norovirus, likely introduced by persons from two different states and subsequently at least two food items, was the probable cause of these illnesses, highlighting the challenge of investigating and controlling norovirus outbreaks. During periods of peak norovirus activity, public health officials should emphasize the importance of appropriate handwashing and the exclusion of ill persons from social gatherings.     

Tuberculosis outbreak associated with a homeless shelter - Kane County, Illinois, 2007-2011

Despite the overall decline in tuberculosis (TB) incidence in the United States to a record low, outbreaks of TB among homeless persons continue to challenge TB control efforts. In January 2010, public health officials recognized an outbreak of TB after three overnight guests at a homeless shelter in Illinois received diagnoses of TB disease caused by Mycobacterium tuberculosis isolates with matching genotype patterns. As of September 2011, a total of 28 outbreak-associated cases involving shelter guests, dating back to 2007, had been recognized, indicating ongoing M. tuberculosis transmission. The subsequent investigation found that all patients were homeless and had been overnight shelter guests. Excess alcohol use was common (82%), and two bars emerged as additional sites of potential transmission. Patients with outbreak-associated TB were treated successfully for TB disease. To prevent future cases of TB, public health officials are implementing a program to offer 12 once-weekly doses of isoniazid and rifapentine under direct observation for treatment of latent tuberculosis infection (LTBI) in this high-risk population. Although the United States has made progress toward TB elimination, this outbreak demonstrates the vulnerability of homeless persons to outbreaks of TB, highlighting the need for aggressive and sustained TB control efforts.     

An outbreak of norovirus gastroenteritis at a swimming club--Vermont, 2004

John Snow's historic investigation of a severe epidemic of cholera traced the cause of infection to a common water source. Today, 150 years later, waterborne diseases remain a public health problem, and similar investigations are used to identify the source of infection. On February 3, 2004, the Vermont Department of Health (VDH) was notified of an outbreak of acute gastroenteritis among children whose only common exposure was attendance at a swimming club the previous weekend (January 31-February 1). This report summarizes the results of an investigation conducted by VDH and CDC, which determined the cause of the outbreak to be a combination of stool contamination, a blocked chlorine feed tube, and multiple lapses of pool-maintenance procedures. The findings underscore the importance of correct pool maintenance for rapid identification of water-quality problems to prevent outbreaks of swimming pool-associated illness.     

Multistate measles outbreak associated with an international youth sporting event--Pennsylvania, Michigan, and Texas, August-September 2007

Measles, a highly infectious viral illness, is no longer endemic in the United States because of high coverage rates with an effective vaccine. However, imported cases continue to cause illness and outbreaks among susceptible U.S. residents. In August 2007, a participant in an international youth sporting event who traveled from Japan to the United States became ill with measles. Because he traveled while infectious to an event with thousands of participants and spectators, an outbreak investigation was conducted in multiple states by state and local health departments in coordination with CDC, using standard measles surveillance case definitions and classifications. This report summarizes the results of that investigation, which identified six additional measles cases that were linked epidemiologically to the index case and two generations of secondary transmission. Viral genotyping supported a single chain of transmission; six of the seven cases were linked by genetic sequencing. U.S. organizers of large-scale events attended by international travelers, especially youths, should consider documentation of adequate participant vaccination. This outbreak highlights the need to maintain the highest possible vaccination coverage in the United States, along with disease surveillance and outbreak-containment capabilities.     

Recurrent multistate outbreak of Salmonella Newport associated with tomatoes from contaminated fields, 2005

Salmonella Newport causes more than an estimated 100,000 infections annually in the United States. In 2002, tomatoes grown and packed on the eastern shore of Virginia contaminated with a pan-susceptible S. Newport strain caused illness in 510 patients in 26 states. In July-November 2005, the same strain caused illness in at least 72 patients in 16 states. We conducted a case-control study during the 2005 outbreak, enrolling 29 cases and 140 matched neighbourhood controls. Infection was associated with eating tomatoes (matched odds ratio 9.7, 95% confidence interval 3.3-34.9). Tomatoes were traced back to the eastern shore of Virginia, where the outbreak strain was isolated from pond water used to irrigate tomato fields. Two multistate outbreaks caused by one rare strain, and identification of that strain in irrigation ponds 2 years apart, suggest persistent contamination of tomato fields. Further efforts are needed to prevent produce contamination on farms and throughout the food supply chain.     

A norovirus outbreak associated with consumption of NSW oysters: implications for quality assurance systems

Norovirus is a common cause of gastroenteritis outbreaks associated with raw shellfish consumption. In Australia there have been several reports of norovirus outbreaks associated with oysters despite the application of regulatory measures recommended by Food Standards Australia New Zealand. This study describes an outbreak of norovirus gastroenteritis following the consumption of New South Wales oysters. In September 2007, OzFoodNet conducted a cohort study of a gastroenteritis outbreak amongst people that had dined at a Port Macquarie restaurant. Illness was strongly associated with oyster consumption, with all cases having eaten oysters from the same lease (RR undefined, p < 0.0001). Norovirus was detected in a faecal specimen. Although no pathogen was identified during the environmental investigation, the source oyster lease had been closed just prior to harvesting due to sewage contamination. Australian quality assurance programs do not routinely test oysters for viral contamination that pose a risk to human health. It is recommended that the feasibility of testing oysters for norovirus, particularly after known faecal contamination of oyster leases, be assessed.     

一起医院住院病人诺如病毒急性胃肠炎暴发疫情的 调查

摘要:目的　调查某医院住院病人腹泻暴发疫情的致病因子,找出传染源和危险因素,提出针对性的预防控制建议,有效控制疫情。方法　采用统一的调查表对病例进行流行病学调查;开展现场卫生学调查并采集便标本,采用RT-PCR对便标本进行诺如病毒核酸检测。结果　调查该病区暴露的住院患者和医务人员135名,发现22名病例,罹患率为16.30%;患者临床表现以腹泻、恶心、呕吐为主,部分患者出现发热症状;不同楼层住院老人罹患率差异无统计学意义（χ2＝0.82,P＞0.05）;住院老人罹患率高于护工（χ2＝5.35,P＜0.05）,不同性别住院老人发病风险相同（χ2＝0.18,P＞0.05）;采集的14份便标本中,8份检测结果为诺如病毒核酸阳性。结论　该次急性胃肠炎暴发疫情是由诺如病毒引起,传染源可能为隐形感染者或病原携带者,病毒通过某种共用媒介传播后再以人-人传播模式进一步扩散,高危人群为住院老人;采取针对性措施后,疫情得以有效控制。     

1起水源性诺如病毒腹泻暴发疫情的现场流行病学调查

目的探讨某工厂1起感染性腹泻暴发疫情的病原体和传播媒介及其防制对策。方法按照病例定义开展病例搜索,采用描述性流行病学方法进行分析,并选择罹患率最高的1个车间,采用回顾性队列研究方法,对调查对象的病例接触史、饮水习惯、就餐习惯等情况进行调查,分析可能的暴露因素。采集部分病例的粪便和肛拭子及蓄水池、直饮机、厕所洗手水等水样进行诺如病毒核酸检测。结果 2009年9月21日至10月3日,该工厂共发生病例634例,总罹患率为4.39%(634/14 439),其中男性罹患率为5.35%(411/7 677),女性罹患率为3.30%(223/6 762),男性高于女性(P<0.01)。A12栋检修科罹患率最高为21.15%(11/52),其次为A23栋总务科20.00%(4/20),第3为A15栋厨房19.57%(27/138)。回顾性队列研究共调查315人,结果显示,接触病例(RR=6.069,5%CI为3.35～10.97)和饮直饮水(RR=2.87,95%CI为1.46～5.65)是危险因素。无论是上班时还是下班时饮直饮水,直饮水饮用量与发病之间均存在剂量反应关系,饮用量越大罹患率越高(P<0.01)。共检测3份粪便1、0份肛拭子样本及13份水样,其中8份病例肛拭子样本和4份水样(2份蓄水池、1份直饮机及1份厕所洗手水的水样)中检测到诺如病毒核酸。结论该起疫情为水源性诺如病毒感染性腹泻暴发疫情。建议由市政水直接提供厂区一切生活饮用水。     

Modeling the role of fomites in a norovirus outbreak

Norovirus accounts for a large portion of the gastroenteritis disease burden, and outbreaks have occurred in a wide variety of environments. Understanding the role of fomites in norovirus transmission will inform behavioral interventions, such as hand washing and surface disinfection. The purpose of this study was to estimate the contribution of fomite-mediated exposures to infection and illness risks in outbreaks. A simulation model in discrete time that accounted for hand-to-porous surfaces, hand-to-nonporous surfaces, hand-to-mouth, -eyes, -nose, and hand washing events was used to predict 17?hr of simulated human behavior. Norovirus concentrations originated from monitoring contamination levels on surfaces during an outbreak on houseboats. To predict infection risk, two dose-response models (fractional Poisson and ₂F₁ hypergeometric) were used to capture a range of infection risks. A triangular distribution describing the conditional probability of illness given an infection was multiplied by modeled infection risks to estimate illness risks. Infection risks ranged from 70.22% to 72.20% and illness risks ranged from 21.29% to 70.36%. A sensitivity analysis revealed that the number of hand-to-mouth contacts and the number of hand washing events had strong relationships with model-predicted doses. Predicted illness risks overlapped with leisure setting and environmental attack rates reported in the literature. In the outbreak associated with the viral concentrations used in this study, attack rates ranged from 50% to 86%. This model suggests that fomites may have accounted for 25% to 82% of illnesses in this outbreak. Fomite-mediated exposures may contribute to a large portion of total attack rates in outbreaks involving multiple transmission modes. The findings of this study reinforce the importance of frequent fomite cleaning and hand washing, especially when ill persons are present.     

1起水源性诺如病毒腹泻暴发疫情的现场流行病学调查

目的探讨某工厂1起感染性腹泻暴发疫情的病原体和传播媒介及其防制对策。方法按照病例定义开展病例搜索,采用描述性流行病学方法进行分析,并选择罹患率最高的1个车间,采用回顾性队列研究方法,对调查对象的病例接触史、饮水习惯、就餐习惯等情况进行调查,分析可能的暴露因素。采集部分病例的粪便和肛拭子及蓄水池、直饮机、厕所洗手水等水样进行诺如病毒核酸检测。结果 2009年9月21日至10月3日,该工厂共发生病例634例,总罹患率为4.39%（634/14 439）,其中男性罹患率为5.35%（411/7 677）,女性罹患率为3.30%（223/6 762）,男性高于女性（P〈0.01）。A12栋检修科罹患率最高为21.15%（11/52）,其次为A23栋总务科20.00%（4/20）,第3为A15栋厨房19.57%（27/138）。回顾性队列研究共调查315人,结果显示,接触病例（RR=6.069,5%CI为3.35～10.97）和饮直饮水（RR=2.87,95%CI为1.46～5.65）是危险因素。无论是上班时还是下班时饮直饮水,直饮水饮用量与发病之间均存在剂量反应关系,饮用量越大罹患率越高（P〈0.01）。共检测3份粪便1、0份肛拭子样本及13份水样,其中8份病例肛拭子样本和4份水样（2份蓄水池、1份直饮机及1份厕所洗手水的水样）中检测到诺如病毒核酸。结论该起疫情为水源性诺如病毒感染性腹泻暴发疫情。建议由市政水直接提供厂区一切生活饮用水。     

Pertussis outbreak in an Amish community--Kent County, Delaware, September 2004-February 2005

Vaccine-preventable disease outbreaks continue to occur among undervaccinated populations in the United States, including contained religious communities. The Amish practice separation from the world through group solidarity and caring for their own. Amish religious doctrine does not prohibit vaccination; however, coverage levels for routine childhood vaccination remain low in many Amish communities. This report describes an outbreak of pertussis in an Amish community in Kent County, Delaware, during September 2004-February 2005, that resulted in 345 cases and affected primarily preschool-aged children. The outbreak underscores the need to promote vaccination in Amish communities through culturally appropriate strategies, such as education and outreach to community leaders.     

Pseudomonas bloodstream infections associated with a heparin/saline flush--Missouri, New York, Texas, and Michigan, 2004-2005

On January 26, 2005, CDC was notified of four cases of Pseudomonas fluorescens bloodstream infection among patients at an oncology clinic in Missouri. All patients had received a heparin/saline flush to prevent clotting of indwelling, central venous catheters. The flushes were preloaded in syringes by IV Flush and distributed by Pinnacle Medical Supply (Rowlett, Texas). On January 31, a nationwide alert against use of all heparin or saline flushes preloaded in syringes by IV Flush was issued by the Food and Drug Administration; the company recalled these products. As of February 15, state and local health departments and CDC had identified a total of 36 Pseudomonas species infections in patients in four states who were administered the heparin/saline flushes from multiple lots. This report describes the ongoing investigation and provides recommendations for investigation and management of potential cases.     

1起疑似食源性诺如病毒感染暴发疫情的流行病学调查

摘要:目的 调查1起小学内出现多名急性胃肠炎病例的感染事件,提出预防控制措施。方法 按照病例定义开展病例搜索,采用描述性流行病学方法和病例对照研究方法进行分析;样本采用RT-PCR方法进行肠道病毒核酸检测。结果 武进区某小学2015年3月2日-11日,出现149例以呕吐症状为主的学生,罹患率为9.0%,3月2日出现发病高峰,病例发病急、班级分布广。现场采集患者肛拭子或呕吐物、对照及食堂工作人员肛拭子、食物和环境样本等共42份,其中2名患者肛拭子、2名患者呕吐物及1名食堂工作人员肛拭子检测出诺如病毒GII型。结论 这是1起由诺如病毒GII型引起的急性胃肠炎暴发疫情,暴发原因可能是由带毒食堂工作人员污染部分食物所致,以食源性传播为主。     

一起高校诺如病毒感染性腹泻暴发疫情流行病学调查

了解某高校诺如病毒感染性腹泻暴发疫情流行病学特征,分析疫情病因,为预防和控制疫情提供参考.方法 采用现场流行病学调查及实验室检测方法,对病例进行回顾性调查.运用描述性统计分析、病例对照研究方法对暴发疫情数据及相关因素进行分析.结果 本次疫情共持续14 d,首发病例发病时间为12月22日13:00,累计发病92例.92例病例中,本科生罹患率为1.57%(62/3 945),研究生罹患率为0.76%(26/3 424),教职工罹患率为0.26%(4/1 560),差异有统计学意义(x2 =23.20,P<0.01).男性罹患率为1.28%(72/5 614),女性罹患率为1.14%(20/1 755),性别差异无统计学意义(x2=0.22,P>0.01).92例病例主要症状为腹泻(73.91%,68/92)、恶心(71.74%,66/92)、腹痛(63.04%,58/92)、呕吐(59.78%,55/92)、发热(42.39%,39/92).学生食堂M餐厅为疫情暴发高危场所(OR=3.72,95%CI=1.67~8.23).实验室检测发现3名学生病例粪便样和1名厨工肛拭子样标本检出诺如病毒,其中2名学生病例均有M餐厅就餐史.结论 该疫情为一起由M餐厅共同暴露引起的诺如病毒感染性腹泻暴发疫情,食物传播为主要传播途径.