Gastroenteritis Outbreaks Caused by Norovirus GII.17, Guangdong Province,China, 2014–2015

In the past decade, the most prevalent norovirus genotype causing viral gastroenteritis outbreaks worldwide, including China, has been GII.4. In winter 2014–15, norovirus outbreaks in Guangdong, China, increased. Sequence analysis indicated that 82% of the outbreaks were caused by a norovirus GII.17 variant.     

Issues Leading to the Recent Outbreaks of Hepatitis A

Since 1996, the incidence of hepatitis A (HAV) had been on the decline due to the development and use of the HAV vaccine. However, recent global outbreaks are occurring among men who have sex with men, illicit drug users, and the homeless. Much of the older population has not been vaccinated, and because of their age, they are more susceptible to complications from this virus. The medical community is challenged with preventing further outbreaks of this infection by promoting pre- and post-exposure immunization, implementing supportive care for those affected by HAV, and providing patient education that will decrease the spread of Hepatitis A.     

Epidemic of Mumps among Vaccinated Persons,the Netherlands, 2009–2012

To analyze the epidemiology of a nationwide mumps epidemic in the Netherlands, we reviewed 1,557 notified mumps cases in persons who had disease onset during September 1, 2009–August 31, 2012. Seasonality peaked in spring and autumn. Most case-patients were males (59%), 18–25 years of age (67.9%), and vaccinated twice with measles-mumps-rubella vaccine (67.7%). Nearly half (46.6%) of cases occurred in university students or in persons with student contacts. Receipt of 2 doses of vaccine reduced the risk for orchitis, the most frequently reported complication (vaccine effectiveness [VE] 74%, 95% CI 57%–85%); complications overall (VE 76%, 95% CI 61%–86%); and hospitalization (VE 82%, 95% CI 53%–93%). Over time, the age distribution of case-patients changed, and proportionally more cases were reported from nonuniversity cities (p<0.001). Changes in age and geographic distribution over time may reflect increased immunity among students resulting from intense exposure to circulating mumps virus.     

Unraveling the drivers of MERS-CoV transmission

With more than 1,700 laboratory-confirmed infections, Middle East respiratory syndrome coronavirus (MERS-CoV) remains a significant threat for public health. However, the lack of detailed data on modes of transmission from the animal reservoir and between humans means that the drivers of MERS-CoV epidemics remain poorly characterized. Here, we develop a statistical framework to provide a comprehensive analysis of the transmission patterns underlying the 681 MERS-CoV cases detected in the Kingdom of Saudi Arabia (KSA) between January 2013 and July 2014. We assess how infections from the animal reservoir, the different levels of mixing, and heterogeneities in transmission have contributed to the buildup of MERS-CoV epidemics in KSA. We estimate that 12% [95% credible interval (CI): 9%, 15%] of cases were infected from the reservoir, the rest via human-to-human transmission in clusters (60%; CI: 57%, 63%), within (23%; CI: 20%, 27%), or between (5%; CI: 2%, 8%) regions. The reproduction number at the start of a cluster was 0.45 (CI: 0.33, 0.58) on average, but with large SD (0.53; CI: 0.35, 0.78). It was >1 in 12% (CI: 6%, 18%) of clusters but fell by approximately one-half (47% CI: 34%, 63%) its original value after 10 cases on average. The ongoing exposure of humans to MERS-CoV from the reservoir is of major concern, given the continued risk of substantial outbreaks in health care systems. The approach we present allows the study of infectious disease transmission when data linking cases to each other remain limited and uncertain.Despite the occurrence of 1,728 laboratory-confirmed cases and 624 deaths (1) since the virus was first isolated in 2012, transmission of the Middle East respiratory syndrome coronavirus (MERS-CoV) remains poorly understood. Dromedary camels play a role in transmission (2), but the nature and extent of human exposure to camels is not well defined. Despite multiple reintroductions from the reservoir, there has been no sign of the continuous exponential growth in human case numbers that is the typical signature of the start of a pandemic. Furthermore, most infections have occurred in Middle Eastern countries on the Arabian Peninsula, with ∼75% of cases reported by the Kingdom of Saudi Arabia (KSA). Spatial expansion to other areas has been limited. Although these simple observations suggest that MERS-CoV is not presently capable of self-sustaining transmission in humans (at least in the Middle East), large clusters of human cases, typically in health care settings, have been documented (3). Notably, in March to May 2014, KSA experienced a large, rapidly growing outbreak affecting many hospitals and spanning multiple regions of the country (Fig. 1) (4, 5).Open in a separate windowFig. 1.The epidemic of MERS-CoV in KSA between January 1, 2013, and July 31, 2014. (A) Biweekly number of MERS-CoV laboratory-confirmed infections per region. (B) Weekly number of cases in the different hospitals and over time. The color of dots indicates the weekly number of cases. Colors on the y axis indicate the region of the hospital. (C) Distribution of the number of cases per cluster. (D) Map of the KSA. Colors in A, B, and C match the color of regions in D.A number of studies have attempted to characterize the human-to-human transmission of MERS-CoV and the contribution of the reservoir from the analysis of specific features of the epidemic—for example, cluster sizes (6), epidemic time series in clusters (7), transmission trees in few large clusters (8, 9), or the proportion of MERS-CoV cases with no known human source of infection (5, 10)—sometimes restricted to one or more large outbreaks (5, 8, 9). Such an approach simplifies inference but comes with a number of limitations. First, by restricting analysis to simple features of the epidemic, strong assumptions about the underlying transmission process are often required, such as assuming that cases with no known source of infection are infected by the reservoir (5–7, 10), that clusters are closed epidemics independent of each other (6, 7, 10), or that transmission rates are constant over time (6). In addition, analysis restricted to large outbreaks may bias estimates of human-to-human transmission upward. A coherent and holistic picture of MERS-CoV epidemic dynamics therefore remains elusive, reflected, for instance, in published estimates of the proportion of infections due to the animal reservoir varying from a few percent (5) to 55% (10).Here, to obtain a comprehensive picture of MERS-CoV transmission dynamics, we developed a general framework to analyze detailed epidemiological records of all MERS-CoV cases reported between January 1, 2013, and July 31, 2014 in KSA, a time frame that included the largest outbreaks of MERS-CoV reported to date. The framework makes it possible to relax the simplifying assumptions often made in past work about the epidemic process (e.g., independence of clusters, unknown sources of infection being interpreted as infections from the reservoir). It builds on methods used to reconstruct transmission trees from case data (11, 12) but greatly expands them by allowing estimation of the generation time distribution, multiple and heterogeneous levels of transmission, and changing risks of infection from a zoonotic reservoir.     

First Canadian outbreak of Enterobacteriaceae-expressing Klebsiella pneumoniae carbapenemase type 3

BACKGROUND:

Organisms expressing Klebsiella pneumoniae carbapenemase (KPC) are found in several regions worldwide but are rarely detected in Canada. The first outbreak of KPC-expressing strains of Enterobacteriaceae clinical isolates in a university-affiliated hospital intensive care unit (ICU) in Canada is described.

METHODS:

Enterobacteriaceae isolates that were flagged by the Vitek 2 (bioMérieux, France) system as possible carbapenemase producers were subjected to the modified Hodge test. Modified Hodge test-positive organisms were analyzed by pulsed-field gel electrophoresis, tested for KPC and other beta-lactamase genes by polymerase chain reaction analysis and underwent subsequent nucleic acid sequencing. Antimicrobial susceptibility profiles were determined by Vitek 2 and Etest (bioMérieux, France). A chart review was conducted to establish epidemiological links.

RESULTS:

During the study period, 10 unique Enterobacteriaceae isolates expressing KPC were detected from nine ICU patients. Five patients had infections (three pneumonias, one surgical site infection, one urinary tract infection). Isolates included Escherichia coli (5), Klebsiella oxytoca (2), Serratia marcescens (2) and Citrobacter freundii (1). Polymerase chain reaction analysis and sequencing confirmed the presence of KPC-3 in all isolates; four also carried TEM, two CTX-M and one CMY-2. The imipenem minimum inhibitory concentrations as determined by Etest ranged from 0.75 μg/mL to ≥32 μg/mL. Pulsed field gel electrophoresis clonal patterns and patient location in the ICU revealed presumptive horizontal transmission events.

CONCLUSIONS:

In the present study, Enterobacteriaceae isolates with KPC are emerging and can result in serious infections. The KPC gene can spread via plasmids to different genera of the Enterobacteriaceae family. The dissemination of KPC in Enterobacteriaceae and the consequences for treatment and infection control measures warrant a high degree of vigilance among clinicians and microbiologists.     

一起学校聚集性肺结核疫情调查

目的了解学生聚集性结核病疫情发生的原因,为学校肺结核病防控提供依据。方法对嵊州市某学校出现病例所有班级学生进行结核菌素(PPD)试验、X线胸部摄片,可疑者CT复查,对X线胸片检查或CT复查异常者给予痰涂片检查抗酸杆菌。结果首发病例为涂阳病人,患者出现症状后在密闭空调环境中与其他同学一起学习2个月,才被明确诊断并离校治疗,增加交叉感染的发病概率。本起疫情通过因症就诊、转诊和筛查共发现肺结核病31例,均为学生病例。其中涂阳肺结核4例、涂阴肺结核25例、结核性胸膜炎2例;18例有临床症状,13例无自觉症状;3-4月份为发病高峰。第1例阳性病例发现时间晚、就诊延误、持续接触、通风不良和学校分班是造成本次聚集性疫情的主要原因。结论应加强学校对传染病的管理,落实晨检和症状监测,以及时发现和隔离结核病病人,预防服药是聚集性肺结核疫情中密切接触者的有效预防手段。     

一起偏远藏族小学校流行性腮腺炎暴发调查与分析

目的调查和分析本次藏族小学校流行性腮腺炎疫情发生原因及处置效果,为今后学校流行性腮腺炎疫情处置与防控提供依据。方法建立病例定义开展病例搜索,并对疫情进行调查和处置。在发病数最多的3个班级开展含腮腺炎成分疫苗(Mumps-containing Vaccine,MuCV)保护效果(Vaccine Effectiveness,VE)的回顾性队列研究。采集现症病例血标本和咽拭子标本,进行腮腺炎病毒IgM抗体和病毒核酸检测。结果共发现26例,罹患率为11.2%,均为学生。临床表现以腮腺肿胀和疼痛(100.0%)、发热(61.5%)、咽痛(53.8%)和头痛(42.3%)为主,均无严重并发症发生。流行曲线提示为人传人模式。男、女学生罹患率分别为12.6%、8.2%(χ~2=1.163,P0.05)。五年级发病人数最多,罹患率为20.5%,其次为一年级(16.3%)和二年级(15.6%)。教室和宿舍内二代病例续发率分别为8.4%、4.0%。回顾性队列研究结果显示,有73.7%的学生接种过一剂次MMR;有、无免疫史学生罹患率分别为16.7%、30.0%,相对危险度(RR)=1.8(95%CI:0.87,3.72),VE=44.4%。实验室检测10例腮腺炎病毒核酸检测均为阳性,腮腺炎病毒IgM抗体阳性6例,阴性4例。结论本次疫情为一起发生在偏远藏族小学校的流腮暴发。采取综合防控措施后,疫情得到了有效控制。建议加强学校传染病的报告与管理,在小学校入学前开展MuCV的加强免疫。