St. Louis encephalitis in southern Ontario: laboratory studies for arboviruses.

The first reported outbreak of St. Louis encephalitis in Canada occurred in the summer of 1975 in southern Ontario -- in the Windsor-Sarnia-Chatham area, the Niagara region and the city of Toronto. Hemmagglutination inhibition and complement fixation testing of serum samples collected during the outbreak confirmed that St. Louis encephalitis virus was the etiologic agent. Furthermore, this virus was isolated from brain tissue of a patient who died. This outbreak was probably an extension of the outbreak that occurred in the United States that summer. It was the first outbreak of arbovirus encephalitis in the province of Ontario.     

Uterine involvement in guineapig salmonellosis

Of 334 mature breeding guineapigs, 53 (15.9%) died in a disease outbreak involving Salmonella typhimurium serotypes 1, 4, 5 and 12 : i : 1,2. The uterus was consistently involved. Nine other Salmonella-free mature female guineapigs when inoculated with a pure isolate from the outbreak, using the subcutaneous, intramuscular or per os route, succumbed to salmonellosis, reproducing signs and lesions observed during the outbreak. Abortion was not recorded during the outbreak despite many pregnant sows being affected. The isolate was sensitive to gentamicin, tetracycline, ampicillin and cefuroxime but resistant to co-trimoxazole, erythromycin and penicillin.     

Outbreak of coagulase negative staphylococcus highly resistant to ciprofloxacin in a leukaemia unit.

OBJECTIVE--To define an outbreak of bacteraemia due to coagulase negative staphylococci highly resistant to ciprofloxacin in a leukaemia unit, investigate the source and mode of spread of the outbreak strain, and assess control measures. DESIGN--The outbreak strain was characterised by five different typing methods. Surveillance of patients, staff, and environment was carried out during the outbreak and five months after control measures were introduced. SETTING--A unit with 10 beds for adults with leukaemia and patients receiving bone marrow transplants. The outbreak occurred during a trial of ciprofloxacin for empirical treatment of neutropenic fevers. INTERVENTIONS--Ciprofloxacin was withdrawn from use in the unit and daily bathing with chlorhexidine gluconate solution started. Main outcome measure--The absence of bacteraemia due to the outbreak strain for five months after control measures. RESULTS--During the study 49 patients developed 21 episodes of bacteraemia due to the outbreak strain, which was ciprofloxacin resistant (minimum inhibitory concentration greater than or equal to 128 mg/l), susceptible to phage 155 A9C, and SII biotype and had characteristic immunoblot and DNA fingerprint features. There was a high amount of colonisation of patients but not staff with this strain, which was also wide spread in the environment. The control measures led to rapid resolution of the outbreak and disappearance of the strain from the unit. CONCLUSIONS--In areas where coagulase negative staphylococcal infections are common doctors must be aware of the possibility of cross infection with single strain, and the availability of more discriminatory methods of typing will facilitate the identification and control of such episodes.     

Genomic Characterization of Listeria monocytogenes Strains Involved in a Multistate Listeriosis Outbreak Associated with Cantaloupe in US

A multistate listeriosis outbreak associated with cantaloupe consumption was reported in the United States in September, 2011. The outbreak investigation recorded a total of 146 invasive illnesses, 30 deaths and one miscarriage. Subtyping of the outbreak associated clinical, food and environmental isolates revealed two serotypes (1/2a and 1/2b) and four pulsed-field gel electrophoresis two-enzyme pattern combinations I, II, III, and IV, including one rarely seen before this outbreak. A DNA-microarray, Listeria GeneChip®, developed by FDA from 24 Listeria monocytogenes genome sequences, was used to further characterize a representative sample of the outbreak isolates. The microarray data (in the form of present or absent calls of specific DNA sequences) separated the isolates into two distinct groups as per their serotypes. The gene content of the outbreak-associated isolates was distinct from that of the previously-reported outbreak strains belonging to the same serotypes. Although the 1/2b outbreak associated isolates are closely related to each other, the 1/2a isolates could be further divided into two distinct genomic groups, one represented by pattern combination I strains and the other represented by highly similar pattern combinations III and IV strains. Gene content analysis of these groups revealed unique genomic sequences associated with these two 1/2a genovars. This work underscores the utility of multiple approaches, such as serotyping, PFGE and DNA microarray analysis to characterize the composition of complex polyclonal listeriosis outbreaks.     

Intervening in pest outbreaks: Simulation studies with the western tent caterpillar

A stochastic model mimicking the behavior of the western tent-caterpillar populations on Vancouver Island was used to study methods of suppressing an outbreak. Since many forest defoliators often receive only one treatment during their outbreak period, we applied a hypothetical single treatment at different times during a simulated outbreak, to assess the influence of timing. Intervening early in the cycle was the best method of suppressing numbers below a tolerable threshold during a particular outbreak. Treatment during the most rapid period of increase was less effective, and treatments at or beyond the peak provided little relief during that particular outbreak. For longer-term protection, however, treating the refugia of a declining population was far superior to less selective intervention. Concentrating the treatment within these refuges decimated the breeding stock surviving there at a time when the population could least afford such injury. Timing and focussing the intervention to obtain that maximal impact thus prolonged the period of suppression during the next outbreak.     

Water-borne outbreak of serous meningitis caused by Echovirus-30 in Belarus

In recent years outbreak of enterovirus infections caused by Echovirus-30 were rather frequently registered in different European countries. A major outbreak caused by this virus took place during the summer-autumn period of 1997 in the city of Gomel, Belarus. Sanitary epidemiological and molecular epidemiological studies made it possible to determine that the outbreak was water-borne. The sequence analysis of Echovirus-30 strains isolated from water and the cerebrospinal fluid of patients revealed a minor divergence between them (0.2%) indicative of their practical identity. The comparison of the Belorussian isolates with the strains isolated in Europe in 1994-1998 also showed a small percentage of differences in their genomes, which showed that the outbreak of Echovirus-30 infection was probably brought to Belarus from the territories of European countries.     

马尾松林节肢动物群落的稳定性

依据广西大青山马尾松林区马尾松毛虫一个暴发周期中食叶、捕食、寄生、刺吸四大类群多样性指数(H′)、丰富度指数(MD)、均匀度指数(J)和害虫与天敌的数量比例的数据,建立突变模型对马尾松林节肢动物群落的稳定性进行研究,并利用湖南桂阳数据对模型进行了检验.结果表明:在马尾松毛虫的整个暴发过程中,暴发区在暴发年的昆虫生物群落处于明显的不稳定状态,而在非暴发年时,群落则处于亚稳定的状态;非暴发区在暴发年处于亚稳定的状态,非暴发年时处于稳定状态.在松毛虫各个发生阶段,当上升期处于不稳定状态时,有可能导致松毛虫的大发生;松毛虫暴发后,节肢动物群落依旧处于不稳定状态,有可能会造成松毛虫的连续暴发,这主要依赖于各种因子的影响.马尾松毛虫暴发呈现非线性、突变性等特点,食叶类群的影响为马尾松毛虫暴发的关键因子,各类群作用均衡的系统比较稳定,虫害暴发是群落结构趋稳调节过程中的强烈外部表现.研究表明,突变模型在检测群落结构稳定性和预测松毛虫发生上有很好的应用前景.     

Epizootiology of an epizootic hemorrhagic disease outbreak in West Virginia

An outbreak of epizootic hemorrhagic disease virus, serotype 2 (EHDV-2) was responsible for localized white-tailed deer (Odocoileus virginianus) mortality in Hardy and Hampshire counties, West Virginia (USA), in the summer and fall of 1993. Using available historical data on regional herd immunity, data opportunistically collected during the epizootic, and postepizootic sampling of hunter-harvested deer, we grossly estimate certain epidemiologic parameters and compare findings to a hypothesis about hemorrhagic disease outbreaks in the Appalachian Mountains. During the epizootic, 57.9 km(2) were actively searched and 228 dead deer were found. Epizootic hemorrhagic disease virus, serotype 2 was isolated from seven of nine deer sampled in Hardy and Hampshire counties. Preepizootic exposure of deer to EHD viruses was unknown, but available data suggest that it was negligible. The geographic distribution of the outbreak was defined by plotting the locations of dead deer found during the outbreak, as well as the locations of deer harvested by hunters after the outbreak that had antibodies to EHDV-2 on a map sectioned into 16.65 km(2) rectangular sections. Sections that included one or more dead deer or hunter-harvested deer with antibodies to EHDV-2 were included in the defined outbreak area. Postoutbreak sampling revealed monospecific EHDV-2 antibodies in 12% of deer harvested by hunters within the defined outbreak area. Based on the available data and accepting certain assumptions, gross calculations suggest that this outbreak appears to have been isolated and probably killed a high percentage of the deer that were infected. This is consistent with the hypothesis that sporadic hemorrhagic disease outbreaks in the Appalachian Mountains are usually localized and severe.     

An outbreak of botulism in wild waterbirds in southern Australia

An outbreak of Type C botulism in waterbirds was investigated at Lake Lalbert in northwestern Victoria, Australia. Total losses were estimated at 1,500 birds, with 80% of affected birds being grey teal (Anas gibberifrons). The outbreak was associated with a falling water level, and extensive decomposition of plant material.     

Effects of fire and spruce beetle outbreak legacies on the disturbance regime of a subalpine forest in Colorado

Aim There is increasing research attention being given to the role of interactions among natural disturbances in ecosystem processes. We studied the interactions between fire and spruce beetle (Dendroctonus rufipennis Kirkby) disturbances in a Colorado subalpine forest. The central questions of this research were: (1) How does fire history influence stand susceptibility to beetle outbreak? And conversely, (2) How does prior occurrence of a beetle outbreak influence stand susceptibility to subsequent fire? Methods We reconstructed the spatial disturbance history in a c. 4600 ha area by first identifying distinct patches in the landscape on aerial photographs. Then, in the field we determined the disturbance history of each patch by dating stand origin, fire scars, dates of mortality of dead trees, and releases on remnant trees. A geographical information system (GIS) was used to overlay disturbance by fire and spruce beetle. Results and main conclusions The majority of stands in the study area arose following large, infrequent, severe fires occurring in c. 1700, 1796 and 1880. The study area was also affected by a severe spruce beetle outbreak in the 1940s and a subsequent low‐severity fire. Stands that originated following stand‐replacing fire in the late nineteenth century were less affected by the beetle outbreak than older stands. Following the beetle outbreak, stands less affected by the outbreak were more affected by low‐severity fire than stands more severely affected by the outbreak. The reduced susceptibility to low‐severity fire possibly resulted from increased moisture on the forest floor following beetle outbreak. The landscape mosaic of this subalpine forest was strongly influenced by the interactions between fire and insect disturbances.     

东亚飞蝗发生的生态因素辨识及监测预测

基于前人研究成果,对中国东亚飞蝗发生的孕灾环境及其主要影响生态因素进行辨识.结果表明:蝗灾的动态变化与气候变化关系密切;飞蝗分布界限受气候带的影响;发生基地具有类似的孕灾环境特征;飞蝗发生发展与水文、气候、土壤和植被等主要生态因素的一定指标阈值有密切关系;传统的飞蝗预测研究多着重分析各生态因子与飞蝗消长的数理统计相关关系,近年多在大尺度气候背景下探讨适宜中长期的预测方法,国内外利用遥感等多种现代化手段对蝗灾进行大范围监测.     

Experiences with vaccination and epidemiological investigations on an anthrax outbreak in Australia in 1997

Between January and February 1997, there was a severe outbreak of anthrax on 83 properties in north-central Victoria, Australia. Vaccination was used as a major tool to control the outbreak by establishing a vaccination buffer zone 30 km by 20 km. In all, 78, 649 cattle in 457 herds were vaccinated in a three week program. In the face of the outbreak, there was a delay before vaccination was able to stop deaths. In the 10 days following vaccination 144 cases of confirmed anthrax occurred and 38 cases occurred more than 10 days after vaccination. When all cattle on at-risk properties were revaccinated in October and early November 1997, there were only two confirmed cases of anthrax in vaccinated seven and nine month old calves in the following anthrax season. Investigations into the epidemiology of the outbreak were unable to establish a single major association for the spread of the disease by flies, biting insects, carrion scavengers, wind, manufactured feed, milk factory tanker routes, veterinary visits, animal treatments, movements of personnel between farms or burning of carcases. The weather conditions in the outbreak area were part of a long dry spell with periods of high daily and night temperatures, continuing high humidity over the period and higher than normal soil temperatures. It is possible that extensive earth works in the district involving irrigated pasture renovation and water channel and drainage renovation could have disturbed old anthrax graves. It is postulated that these works released spores that were dispersed in the preceding wet winter across poorly drained areas that formed the axis for the outbreak. The earth moving renovations establishing irrigation in the area were conducted in the late 1890s, and before the occurrence of anthrax outbreaks were recorded. The axis of the outbreak was the major stock route for cattle and sheep moving from southern Victoria to northern Victoria and southern New South Wales, and undoubtedly there would have been extensive anthrax outbreaks before vaccine became available in the 1890s. In respect of other outbreaks, the events in Victoria most resembled outbreaks of anthrax recorded in the United States of America in the 1950s, 1960s and 1970s.     

Climate change could alter the distribution of mountain pine beetle outbreaks in western Canada

Climate change can markedly impact biology, population ecology, and spatial patterns of eruptive insects due to the direct influence of temperature on insect development and population success. The mountain pine beetle Dendroctonus ponderosae (Coleoptera: Curculionidae), is a landscape‐altering insect that infests forests of North America. Abundant availability of host trees due to altered disturbance regimes has facilitated an unprecedented, landscape‐wide outbreak of this pest in British Columbia and Alberta, Canada, during the past decade. A previous outbreak in the 1980s, in central British Columbia, collapsed due to host depletion and extreme cold weather events. Despite the importance of such extreme weather events and other temperature‐related signals in modulating an outbreak, few landscape‐level models have studied the associations of extreme cold events with outbreak occurrences. We studied the individual associations of several biologically‐relevant cold temperature variables, and other temperature/degree‐day terms, with outbreak occurrences in a spatial‐temporal logistic regression model using data from the current outbreak. Timing, frequency, and duration of cold snaps had a severe negative association with occurrence of an outbreak in a given area. Large drops in temperature (>10°C) or extreme winter minimum temperatures reduced the outbreak probability. We then used the model to apply eight different climate change scenarios to the peak year of the current outbreak. Our scenarios involved combinations of increasing annual temperature and different variances about this trend. Our goal was to examine how spatial outbreak pattern would have changed in the face of changing thermal regime if the underlying outbreak behaviour remained consistent. We demonstrate that increases in mean temperature by 1°C to 4°C profoundly increased the risk of outbreaks with effects first being manifested at higher elevations and then at increasing latitudes. However, increasing the variance associated with a mean temperature increase did not change the overall trend in outbreak potential.     

Outbreak of Shigella sonnei in a rural hotel in La Gomera, Canary Islands, Spain.

Shigella sonnei is a significant cause of gastroenteritis in both developing and industrialized countries. Knowledge of the diversity and antimicrobial susceptibility of the bacterium may be helpful in the management of both individual cases and outbreaks. This study was undertaken to evaluate the molecular epidemiology of an outbreak of diarrhea due to S. sonnei. The outbreak involved 14 of 28 (50%) tourists in a small rural hotel in La Gomera, Canary Islands, Spain. All of the S. sonnei isolates recovered had the same antimicrobial susceptibility and pulsed-field gel electrophoresis patterns, suggesting that the outbreak was produced by a single strain.     

Hepatitis A outbreak in Anchorage,Alaska, traced to ice slush beverages.

The Alaska Department of Health and Social Services investigated a community outbreak of hepatitis A in Anchorage. A total of 57 persons who had hepatitis A between June and September 1988 were studied. Patients ranged from 1 to 54 years of age. A market was implicated as the source of the outbreak. An employee who prepared beverage mixtures in a bathroom was a contact of a person who had had hepatitis A 2 months before the outbreak; the employee was reported to have been jaundiced 3 to 4 weeks before the peak of the outbreak. The administration of immune globulin had an efficacy of 100% (95% confidence limits 69, 100%) in preventing hepatitis A among household contacts of primary cases. Similar beverages are sold by convenience markets and many other businesses nationwide. It is important to ensure that safe food-handling practices are followed by such establishments.     

温州市第三代二化螟大发生原因分析

第 3代二化螟大发生是由防治第 2代时失去最佳防治适期 ,而使其绝大部分幼虫存活下来 ,成为第 3代有效虫源所致 ;二是发生时间早 ;三是早稻收割期天气差 ,使 2代向 3代的转化率提高。1998温州市第 3代二化螟大发生正是由于上述 3个原因综合的结果 ,发生面积达 13.5万公顷 ,占当年晚稻面积的 95%以上 ,防治面积达 18万公顷 ,为该市近 10年来所少见。     

Dynamics of two separate but linked HIV-1 CRF01_AE outbreaks among injection drug users in Stockholm, Sweden, and Helsinki, Finland

Detailed phylogenetic analyses were performed to characterize an HIV-1 outbreak among injection drug users (IDUs) in Stockholm, Sweden, in 2006. This study investigated the source and dynamics of HIV-1 spread during the outbreak as well as associated demographic and clinical factors. Seventy Swedish IDUs diagnosed during 2004 to 2007 were studied. Demographic, clinical, and laboratory data were collected, and the V3 region of the HIV-1 envelope gene was sequenced to allow detailed phylogenetic analyses. The results showed that the Stockholm outbreak was caused by a CRF01_AE variant imported from Helsinki, Finland, around 2003, which was quiescent until the outbreak started in 2006. Local Swedish subtype B variants continued to spread at a lower rate. The number of new CRF01_AE cases over a rooted phylogenetic tree accurately reflected the transmission dynamics and showed a temporary increase, by a factor of 12, in HIV incidence during the outbreak. Virus levels were similar in CRF01_AE and subtype B infections, arguing against differences in contagiousness. Similarly, there were no major differences in other baseline characteristics. Instead, the outbreak in Stockholm (and Helsinki) was best explained by an introduction of HIV into a standing network of previously uninfected IDUs. The combination of phylogenetics and epidemiological data creates a powerful tool for investigating outbreaks of HIV and other infectious diseases that could improve surveillance and prevention.     

呼吸内科重症监护室一起多重耐药鲍曼不动杆菌感染暴发的调查

目的及时发现医院感染暴发苗头,查找感染源,切断传播途径,最大限度减少医院感染发生。方法对2009年4月26～28日期间RICU发生的4例鲍曼不动杆菌感染病例进行聚集感染危险因素调查,采集标本进行目标菌检测,应用ERIC—PCR技术对聚集病例和散发病例菌株进行基因同源性分析,采取综合性防控措施进行医院感染具体干预。结果4例患者确定为医院感染病例,4例患者均有气管插管操作经历,3例患者环境卫生学检测存在耐药谱相同的鲍曼不动杆菌,ERIC—PCR分析4例患者检出的鲍曼不动杆菌具有基因同源性,确定为医院感染暴发。严格执行隔离防护措施和后续加强上呼吸机患者管理,未再出现聚集病例。结论医院感染暴发危及患者医疗安全,应用分子生物学分析手段可以促进医院感染防控措施的效果;加强上呼吸机患者的管理,加强手卫生的管理可以有效防控医院感染聚集暴发。     

Fatal,virus-associated peripheral neuropathy and retinopathy in farmed Penaeus monodon in eastern Australia. II. Outbreak descriptions

Outbreaks of 'peripheral neuropathy and retinopathy' (PNR) occurring during 2 consecutive growout periods (typically October-April) are described for an intensive Penaeus monodon farm in eastern Australia. In the 1998/99 growout period, outbreaks graded minor to severe occurred in 22 of 25 ponds, 12 to 25 wk post-stocking. In the severely affected index pond, harvested 8 wk after outbreak recognition in mid-January, estimated survival for the period late December to harvest was 50%. Minor to moderate losses could be attributed to PNR in the other ponds. Mean survival over the same period for the 14 ponds harvested within 5 wk of outbreak recognition was 93% (83 to 100%); for the 7 ponds harvested 5 to 8 wk after outbreak recognition was 79% (67 to 92%) and for the 3 unaffected ponds was 90% (86 to 95%). Analysis indicated a significantly lower risk (Fisher's exact p = 0.016) of an outbreak in the 2 ponds stocked only with postlarvae from one hatchery (D) versus the 18 ponds stocked only with postlarvae from 3 other hatcheries (A, B and C). In the 1999/2000 growout period, minor to severe PNR outbreaks occurred in all 26 ponds, each stocked with postlarvae from the same hatchery (E), 19 to 21 wk post-stocking. Stocking date in 1999/2000 appeared to influence PNR outbreak severity; for ponds stocked on 2 of the 7 stocking dates versus those stocked on remaining dates, the crude relative risks (CRR) of a severe outbreak, or either a moderate or severe outbreak, were 11.25 (1.55 < CRR < 81.40) and 2.63 (1.30 < CRR < 5.31), respectively. Although inconclusive, study findings are consistent with the hypothesis that 'gill-associated virus' (GAV), the putative causal pathogen identified in a separate pathological study, entered ponds via postlarvae, and that prevalence and/or severity of infection within postlarval batches influenced outbreak severity. The generally high survival in ponds harvested soon after outbreak recognition, together with PNR prevalence of approximately 50% in prawns collected from 4 ponds 7 wk before those ponds were recognised as affected, also suggest that GAV is highly infectious and that PNR has a relatively long incubation period and/or clinical course.     

黑龙江省草地螟第三个暴发周期特点及成因分析

草地螟Loxostege sticticalisL.是我国北方农牧区重要突发性害虫,黑龙江省是主要迁入危害区,自1996年进入第3个暴发周期后,每年均有不同程度发生危害,该周期比上一周期发生时间提前5~7d,周期持续时间也延长了5年。此周期内该省草地螟累计发生面积近1 333万hm2次,比上个周期增加了近800万hm2,草地螟1代幼虫密度最高达每m210 000头以上,尤其2004年在该省大范围内达到特大发生,有13个县(市)田间百步惊蛾达到万头以上,个别高达50 000头以上。作者根据这一周期草地螟发生实况,分析了草地螟种群暴发与气候条件变暖的关系,包括天气、湿度、种植结构、天敌等因素的影响,为草地螟综合治理提供依据。