Epidemic Focus Research Articles

Evaluation of malaria elimination surveillance in Liyang City from 2010 to 2016

To evaluate the effect of malaria elimination monitoring in Liyang City, so as to provide the evidence for formulating control strategies and measures of malaria elimination. The monitoring data about the epidemic situation, blood tests of feverish patients and epidemiology investigation of individual malaria patients in Liyang City from 2010 to 2016 were collected and analyzed by the descriptive epidemiology method. From 2010 to 2016, there were 67 malaria cases in total. Totally 39 196 feverish patients had blood tests for Plasmodium, and 65 of them showed positive and the positive rate was 0.17%. The other 2 cases of microscopy negative were treated with anti-malarial drugs by themselves after the onset of fever, and no Plasmodium was detected in the microscopy, but the tests with malaria rapid diagnostic kit (RDTs) were positive. Among all the 67 cases, there were 49 falciparum malaria cases, 13 ovale malaria cases and 5 vivax malaria cases. All the 67 malaria cases were imported, and the number of cases from Africa was 63 (94.03%). Totally 97.01% (65/67) of the malaria patients were male and most of them were young adults. The patients aged 30 to 49 years accounted for 73.13% (49/67) and 80.60% (54/67) of them were farmers. There were malaria cases in all the 10 towns of the city, and the time of onset had no obvious seasonal characteristics. The timely rate of case report, timely rate of blood film review, standardized treatment rate, epidemiological case investigation rate, and epidemic focus investigation and disposal rate were all 100%. There were 18 076 people with the active case investigation, but no malaria parasite positive carriers were found. The mosquito vector monitoring was performed with the methods of mosquito trap lamp and human bait half night trap, and 187 and 78 Anopheles mosquitoes were captured respectively, and all the parasites were Anopheles sinensis. A total of 88 person-times were performed for the Plasmodium examinations with microscopy and RDTs (one blood sample, two detections) in Liyang City Center for Disease Prevention and Control from 2012 to 2016, and 35 person-times were positive, including 28 person-times of Plasmodium falciparum and 7 person-times of P. ovale, and there was no statistically significant difference between the detection rates of P. falciparum, and P. ovale (adjusted χ2 = 0.05, P > 0.05). There were 34 RDTs positive cases, including 14 cases of malignant malaria, and 17 cases of malignant malaria or mixed infections of P. falciparum with other three kinds of Plasmodium parasites, and 3 cases of single infection or mixed infections of other three kinds of Plasmodium parasites, and there was a statistically significant difference among them in the positive RDTs detection rates (adjusted χ2 = 13.75, P < 0.05). There are still imported malaria cases and there is the risk of malaria retransmission in Liyang City. Therefore, it is necessary to strengthen the malaria surveillance work and the management of infectious sources, so as to consolidate the achievements of malaria elimination in the future.

Current State of Cholera Specific Prophylaxis

The threat of cholera spread beyond the borders of endemic countries and the realness of the emergence of introduced epidemic foci remain the actual problems and neccessitate continuous development of specific prophylaxis of this disease. The review is dedicated to the analysis of the effectiveness of licensed cholera vaccines as well as to possible perspectives of the advancement of cholera specific prophylaxis.

Outbreak of Pneumonic Plague in 2017 on Madagascar

The causes of emergence and development of pneumonic plague outbreak in 2017 on Madagascar were analyzed. Summarized were the literature data, characterizing the spatial and biocoenotic structure of natural plague focus on Madagascar, assessed were the risk factors of plague infection among rural and urban population of the island, as well as the properties of Yersinia pestis strains isolated there in the XX century. It is substantiated that the distinctive type of plague outbreaks on Madagascar is a rural one. It is demonstrated that one of the main causes of wide spread of plague in 2017 is importation of the infection from central regions of the Republic of Madagascar into big cities with further formation of multiple epidemic foci. Confirmed was the circulation of Y. pestis strains that belong to the third branch of irradiation of oriental biovar (1.ORI3). Discussed are the issues of diagnostics and treatment of plague in epidemic foci in the territory of the Republic of Madagascar. The evidence is provided to the fact that the plague outbreak in 2017 on Madagascar is the consequence of a lower surveillance level, first and foremost undervaluation of specific and non-specific prophylaxis capacities regarding this infection.

Measles. Characteristics of the Epidemic Process and its Determinant in Real-Time Conditions (on the Example of a Measles outbreak in Yekaterinburg in 2016)

Introduction. Measles still poses a threat to the inhabitants of the planet. In different regions of the world and the Russian Federation are recorded instances of contamination and subsequent infection with formation of foci with a significant number of victims. Measles has a high reproduction rate of the infection. The purpose of this study was to determine the main characteristics of the epidemic process of measles and its determinants in realtime for direct and indirect control of epidemic process. Materials and methods. The authors analyzed the data of official registration of the incidence of measles the population of Ekaterinburg from 1988 to 2016, and medical records of cases of measles in 2016. We used epidemiological, clinical and statistical research methods. Results. The authors found that the epidemic process of measles has undergone significant changes. Measles was not registered in the city from 2001 to 2015, the unit drifts measles-endemic territories didn't leak. However, the situation changed at the end of 2016. It was 72 clinically and laboratory confirmed case of measles in a period of 11 weeks. The largest proportion of cases were in children who are not vaccinated against measles. The average age of infection in children was 3.8 years. 59 measles epidemic foci were formed during the flash. Foci were registered in families, educational institutions and health care organizations. The most active spread of the infection was in medical organizations. The spread was associated with the presence of susceptible children and adults, serious shortcomings in terms of timely diagnostics of measles in the first and subsequent cases, violations in the organization of antiepidemic measures. Conclusion. 1. Despite positive shifts in the direction of measles elimination, it remains an actual infection, reserving opportunities for distribution among unvaccinated adults and children. 2. A special feature of the outbreak of measles in the territory of Yekaterinburg was the spread in medical organizations with the formation of secondary foci along the routes of following sick children and adults. The share of foci in medical organizations was 15.2% of the number of all foci, and the number of cases in any - 70.8% of registered cases.3. The significance of previously vaccinated cases as potential sources of infection in the foci is not high, the incidence rate when in contact with them is 0.53 ± 0.15, whereas in contact with previously not vaccinated - 7.94 ± 0.56.

TRANSFER OF DANGEROUS VIRAL INFECTIONS IN THE NON-ENDEMIC AREA

Epidemic data are presented, possible causes analyzed and the dangers of observed in recent years expansion of existing areas of viral infections, including the introduction of the agent to the non-endemic area, evaluated. At the present time there is a significant expansion of the ranges of some zooantroponozes pathogens, particular filovirus Ebola and arboviruses - Rift Valley fever, Zika, Chikungunya. When extending the boundaries of epidemic foci in the new territory for the pathogen, can occur aggravating of clinical manifestations of the disease and increase mortality among the indigenous population. Extremely hazardous exotic viral hemorrhagic fever (Ebola, Marburg, Lassa) when transfer with sick people in some cases, can cause contamination of the contact persons. Rift Valley fever - one of the most aggressive arboviruses, in the case of importation can form stable epidemic foci. Transfer of Zika fever in the territory of the Russian Federation has not represent substantial epidemiological value. Epidemiological factors, essential for the formation of new areas of pathogens may include the presence of permissive candidates in natural hosts and vectors, the climatic conditions. Role of socio-economic factors is significant. Among of environmental factors is the important role of some trace elements, including selenium, involved in the regulation of homeostasis and which faults occur in the upward virulence virus mutating. In parts of Africa and Asia, with soils poor in selenium, were first introduced pathogens or highly virulent strains of influenza A, SARS, Ebola and of SIV, and drifts on these and similar areas have led to an increase in the virulence of viruses.

The Experience of the Retrospective Epidemiological Analysis of Outbreaks of Pertussis in the Moscow Suburbs

Background Pertussis outbreaks are continuously observed in different countries despite many years of specific prophylaxis measures for this infection, use of whole-cell and acellular vaccines and use of different schemes of immunization. In our country, even with the overall morbidity stabilization, outbreaks of pertussis continue to be recorded even in regions where the situation was satisfactory previously. As a rule, the majority of epidemic pertussis foci were limited to 1 case of disease (without spread of infection) -86.4% in average. The prevalence of mild clinical forms of disease that are hard to detect, poor effectiveness of the bacteriological method used for examination of exposed persons, and a decrease in the number of examined persons suggest underreporting of whooping cough cases. The most reliable information on the epidemic process manifestations of pertussis can be obtained during outbreaks. Therefore, we conducted a review of outbreaks of pertussis in a small town of district subordinance. Materials and methods As methods of our study we used retrospective epidemiological analysis, serological and molecular genetic methods. The main sources of information were emergency reports and epidemiological investigation of pertussis. Results and discussion From July 28, 2015 to March 24, 2016 year 58 cases of pertussis were observed. Three secondary schools, two grammar schools, five kindergartens, one trade school and the children not attending any educational facility were affected by the outbreak of whooping cough. In the end, during the outbreak, there were 6 foci in kindergartens, 1 focus in the trade school, 18 -in secondary schools, 53 household foci, with the number of patients ranging from 1 to 18. Age distribution was as follows: 50 children (86.2%), 6 adolescents (10.3%) and 2 (3.5%) adults. Among those, 9 people have not been vaccinated against pertussis, with three more also considered un-vaccinated due to an unknown vaccination status, and three children received just one dose of the DPT vaccine; 43 patients had been vaccinated against pertussis, including one who received three doses of the vaccine, 41 had a booster pertussis vaccination. In most cases the source of infection could not be established. 44 patients had a mild form of whooping cough, while 1 case was a combination of pertussis and parapertussis, and 13 patients had medium or severe form of the disease. Conclusion The almost simultaneous identification of whooping cough cases by a number of institutions suggest the existence hidden pertussis cases. Despite the fact that vaccination in household foci is not indicted, it is still possible to prevent the spread of pertussis. It was enough to suspect whooping cough in children coughing for more than 7 days and order laboratory examination to avoid any prolonged stay of an infection source in an organized collective. Overcrowded accommodation in neighbourhoods, close contacts of children at neighborhood playgrounds in neighborhoods and supplementary education classes were the factors that allowed the infection to spread to many institutions of the city.

Temporal and spatial distribution characteristics in the natural plague foci of Chinese Mongolian gerbils based on spatial autocorrelation

BackgroundThe nest flea index of Meriones unguiculatus is a critical indicator for the prevention and control of plague, which can be used not only to detect the spatial and temporal distributions of Meriones unguiculatus, but also to reveal its cluster rule. This research detected the temporal and spatial distribution characteristics of the plague natural foci of Mongolian gerbils by body flea index from 2005 to 2014, in order to predict plague outbreaks.MethodsGlobal spatial autocorrelation was used to describe the entire spatial distribution pattern of the body flea index in the natural plague foci of typical Chinese Mongolian gerbils. Cluster and outlier analysis and hot spot analysis were also used to detect the intensity of clusters based on geographic information system methods. The quantity of M. unguiculatus nest fleas in the sentinel surveillance sites from 2005 to 2014 and host density data of the study area from 2005 to 2010 used in this study were provided by Chinese Center for Disease Control and Prevention.ResultsThe epidemic focus regions of the Mongolian gerbils remain the same as the hot spot regions relating to the body flea index. High clustering areas possess a similar pattern as the distribution pattern of the body flea index indicating that the transmission risk of plague is relatively high. In terms of time series, the area of the epidemic focus gradually increased from 2005 to 2007, declined rapidly in 2008 and 2009, and then decreased slowly and began trending towards stability from 2009 to 2014. For the spatial change, the epidemic focus regions began moving northward from the southwest epidemic focus of the Mongolian gerbils from 2005 to 2007, and then moved from north to south in 2007 and 2008.ConclusionsThe body flea index of Chinese gerbil foci reveals significant spatial and temporal aggregation characteristics through the employing of spatial autocorrelation. The diversity of temporary and spatial distribution is mainly affected by seasonal variation, the human activity and natural factors.

Analysis of overseas imported malaria and implication for prevention and control strategy in Shijiazhuang City from 2012 to 2015

Objective To analyze the overseas imported malaria situation of Shijiazhuang City from 2012 to 2015, so as to provide the evidence for exploring the prevention and control strategy. Methods The data of overseas imported malaria were collected and analyzed with the descriptive method including Plasmodium species, population characteristics, epidemic focus distribution, onset time, diagnosis and treatment in Shijiazhuang City from 2012 to 2015, and the time from the onset to first medical visit, time from first medical visit to being diagnosed, and time from onset to being diagnosed of different Plasmodium species were analyzed respectively with the statistical analysis method. Results A total of 92 overseas imported malaria cases were reported in Shijiazhuang City from 2012 to 2015, including 88 cases from African countries (falciparum malaria taking 53.41%), and 4 cases from Southeast Asian and other countries (vivax malaria taking 50%). Eighty-nine cases were distributed in 28 counties (districts) of 6 cities in Hebei Province, except 2 persons with foreign nationalities and 1 with Anhui Province census register. The male and young adults were dominant. The median time from the onset to seeing a doctor was one day and the median time from seeing a doctor to being diagnosed was five days. Most cases were reported by the Fifth Hospital of Shijiazhuang which was the sentinel hospital. Totally 42.39% of the cases were misdiagnosed when the first visit to a doctor. All of the cases were laboratory confirmed and 100% of them received the standard treatment after diagnosis. Conclusions The overseas imported malaria cases are increasing rapidly with years and the malignant malaria cases were more than other malaria cases in Shijiazhuang City. It is necessary to further strengthen the long-term cooperation mechanism between the medical institutions and the entry-exit inspection and quarantine department. The technician training should be strengthened to avoid the severe cases and death cases.

Environmental Factors as Key Determinants for Visceral Leishmaniasis in Solid Organ Transplant Recipients, Madrid, Spain.

During a visceral leishmaniasis outbreak in an area of Madrid, Spain, the incidence of disease among solid organ transplant recipients was 10.3% (7/68). Being a black person from sub-Saharan Africa, undergoing transplantation during the outbreak, and residing <1,000 m from the epidemic focus were risk factors for posttransplant visceral leishmaniasis.

Pigsties near dwellings as a potential risk factor for the prevalence of Japanese encephalitis virus in adult in Shanxi, China

BackgroundThe increasing trend of adult cases of Japanese encephalitis (JE) in China, particularly in northern China, has become an important public health issue. We conducted an epidemiological investigation in the south of Shanxi Province to examine the relationships between mosquitoes, Japanese encephalitis virus (JEV), and adult JE cases.MethodsMosquito specimens were collected from the courtyards of farmers’ households and pig farms in Shanxi Province. Mosquitoes were pooled, homogenized, and centrifuged. Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect mosquito-borne arbovirus genes in homogenates. Specimens positive for these genes were inoculated into the baby hamster kidney cell line (BHK-21) to isolate virus. Minimum infection rate was calculated and phylogenetic analyses were performed.ResultsA total of 7 943 mosquitoes belonging to six species in four genera were collected; Culex tritaeniorhynchus accounted for 73.08% (5 805/7 943), C. pipiens pallens for 24.75% (1 966/7 943), and the remaining 3% (104/ 7943) consisted of Anopheles sinensis, Aedes vexans, Ae. dorsalis, and Armigeres subalbatus. Sixteen pools were positive for JEV based on RT-PCR using JEV pre-membrane gene nested primers. Phylogenetic analyses showed that all JEVs belonged to genotype I; two pools were positive using Getah Virus (GETV) gene primers. In addition, one JEV strain (SXYC1523) was isolated from C. pipiens pallens specimens. These results indicate that the minimum infection rate of JEV in mosquito specimens collected from the courtyards of farmers’ households with pigsties was 7.39/1 000; the rate for pig farms was 2.68/1 000; and the rate for farmers’ courtyards without pigsties was zero.ConclusionsThe high-prevalence regions of adult JE investigated in this study are still the natural epidemic focus of JEV. Having pigsties near dwellings is a potential risk factor contributing to the prevalence of adult JE. To prevent the occurrence of local adult JE cases, a recommendation was raised that, besides continuing to implement the Expanded Program on Immunization for children, the government should urge local farmers to cease raising pigs in their own courtyards to reduce the probability of infection with JEV.

Establishment of first engineering specifications for environmental modification to eliminate schistosomiasis epidemic foci in urban areas

Snail control is a key link in schistosomiasis control, but no unified methods for eliminating snails have been produced to date. This study was conducted to explore an engineering method for eliminating Oncomelania hupensis applicable to urban areas. The engineering specifications were established using the Delphi method. An engineering project based on these specifications was conducted in Hankou marshland to eliminate snails, including the transformation of the beach surface and ditches. Molluscicide was used as a supplement. The snail control effect was evaluated by field investigation. The engineering results fulfilled the requirements of the design. The snail density decreased to 0/0.11m2, and the snail area dropped to 0m2 after the project. There was a statistically significant difference in the number of frames with snails before and after the project (P<0.05). Snails were completely eliminated through one year of continuous monitoring, and no new snails were found after a flood disaster. This study demonstrates that engineering specifications for environmental modification were successfully established. Environmental modification, mainly through beach and ditch remediation, can completely change the environment of Oncomelania breeding. This method of environmental modification combined with mollusciciding was highly effective at eliminating snails.

Study of epidemic area on Tsutsugamushi disease in Taizhou from 2013 to 2014

Objective: To study the epidemiological characteristics of tsutsugamushi disease, and to confirm the existence of the disease's epidemic foci in Taizhou. Methods: From 2013 to 2014, Dongxing town hospital and Xingqiao town hospital were selected as specimen collection sites in Jingjiang city. Blood samples (5 ml) were collected from 40 patients with acute tsutsugamushi disease. A total of 59 rodents were captured with cage night method in the survey sites at 5, 7, 9, 10, and 11 months in 2013, from which, the spleen, liver, and kidney specimens were selected. Chigger mites were captured by small blackboard method and from the ears of the captured rodents. A total of 226 small blackboards were laid, 27 mites were captured, and the samples were grounded into suspension. Nested-polymerase chain reaction and cell and tissue culture techniques were used to test the specimen from the probable patients, host animals and chigger mites. Results: Among the 40 acute tsutsugamushi disease blood samples, 29 were found to meet the test requirements, 17 were positive for orientia tsutsugamushi nucleic acid with 59% of the positive rate, and 1 stran orientia tsutsugamushi was isolated. 59 rats were captured and the density of mice was 5.5%. Among them, there were 26 Mus musculus (2.4%), 18 Rattus flavipectus (1.7%) and 15 Smelly shrew (density 1.4%). 1 Smelly shrew was tested positive for orientia tsutsugamushi nucleic acid, and the negative results were found in the other rodent specimens. 27 Chigge mites were collected by small blackboard method and the density of mites was 0.12 for each blackboard, among which 3 larvae and 24 nymphs were found. 33 Chigger mites were collected from the ears of 3 Smelly shrew, and the density of the mite was 11 per mouse. All the captured Chigger mites were identified as Leptotrombidium scutellare and 1 group of specimens of Chigger mites from the external environment were positive for orientia tsutsugamushi nucleic acid. Conclusion: There was a high density of mice in the epidemic area from May to November and the species of the chigger mites were Chigger mites in Taizhou. The nucleic acid of the oriental tsutsugamushi was detected in the patients with acute scrub typhus, rodents and vectors. According to the above-mentioned results, it was considered that the scrub typhus epidemic area of Taizhou city has the natural foci of scrub typhus.

SONNEI DYSENTERY MORBIDITY IN KHABAROVSK AND KHABAROVSK REGION DUE TO ATYPICAL MANNITOL-NEGATIVE CAUSATIVE AGENT

Determine features of epidemic process (EP) of Sonnei dysentery in Khabarovsk Region in 2012 - 2014 due to atypical causative agent. Detailed characteristics of 161 cultures of Shigella sonnei isolated from 81 patients from epidemic focus in children boarding school in Bikin as well as from 22 patients from sporadic and group foci of dysenteryin Khabarovsk (biochemical type, colicin-genotype, spectrum of drug resistance) is given. Molecular-biologic subtyping was carried out for 11 strains by Pulsed Field Gel Electrophoresis method (PFGE). Materials of observation of a prolonged foci of Sonnei dysentery with contact-domestic transmission route of the infection in children boarding house for disabled (October 2012 - September 2014) are presented. The diseases are etiologically connected with atypical mannitol- negative types of shigella isolated for the first time in 40 years of observation in Khabarovsk region. Epidemic process of shigellosis was supported by prolonged carriership of the causative agent in patients and special contingent ofthe nursing home. Shigella cultures isolated in the focus belonged to the same colicin-genotype and 2 distinct drug resistance clones, but a single genotype established by PFGE method. Results of the studies give evidence on the importance of determi- nation of traditional phenotypic and contemporary genotypic variants of shigella and the neces- sity of search for arguments, additional methodic approaches for establishing similarities and differences of shigella isolates from within the same outbreak of the diseases as well as for com- parison of strains circulating in different territories.

Spatial Analysis of the Human Immunodeficiency Virus Epidemic among Men Who Have Sex with Men in China, 2006-2015.

Studies have shown a recent upsurge in human immunodeficiency virus (HIV) burden among men who have sex with men (MSM) in China, especially in urban areas. For intervention planning and resource allocation, spatial analyses of HIV/AIDS case-clusters were required to identify epidemic foci and trends among MSM in China. Information regarding MSM recorded as HIV/AIDS cases during 2006-2015 were extracted from the National Case Reporting System. Demographic trends were determined through Cochran-Armitage trend tests. Distribution of case-clusters was examined using spatial autocorrelation. Spatial-temporal scan was used to detect disease clustering. Spatial correlations between cases and socioenvironmental factors were determined by spatial regression. Between 2006 and 2015, in China, 120 371 HIV/AIDS cases were identified among MSM. Newly identified HIV/AIDS cases among self-reported MSM increased from 487 cases in 2006 to >30 000 cases in 2015. Among those HIV/AIDS cases recorded during 2006-2015, 47.0% were 20-29 years old and 24.9% were aged 30-39 years. Based on clusters of HIV/AIDS cases identified through spatial analysis, the epidemic was concentrated among MSM in large cities. Spatial-temporal clusters contained municipalities, provincial capitals, and main cities such as Beijing, Shanghai, Chongqing, Chengdu, and Guangzhou. Spatial regression analysis showed that sociodemographic indicators such as population density, per capita gross domestic product, and number of county-level medical institutions had statistically significant positive correlations with HIV/AIDS among MSM. Assorted spatial analyses revealed an increasingly concentrated HIV epidemic among young MSM in Chinese cities, calling for targeted health education and intensive interventions at an early age.

The Emerging Questions from the Current Epidemiology of Visceral Leishmaniasis in South Sudan: A Cross-sectional Study Design

Leishmaniasis is endemic in South Sudan with at least two outbreaks reported since 1984. A major impediment to effective control is the paucity of epidemiological data to inform prevention and control efforts. The intent of this study is to describe the epidemiology of the disease to inform prevention and control interventions. An analytical cross-sectional design was applied to the National Leishmaniasis Surveillance database from 2009 to 2013 to determine trends and influences on risk of death. Leishmaniasis cases were defined according to national disease surveillance protocols. Point estimates at 95% C.I. and regression estimates of odds and R2 of risks outcomes were determined. The prevalence (cases per 10,000) of visceral leishmaniasis (VL) in the endemic areas varied from 0.14 in 2009 to 5.13 in 2011 and 0.2 in 2013. During this period, 2,466 cases were reported of which 89.5% (95% C.I. 88.2-90.6) had primary visceral leishmaniasis while 7.1% (95% C.I 6.2-8.2) were relapse cases. Following treatment, 90.7% (95% C.I. 89.4-91.8) of cases were cured, with a case fatality of 3.7% (95% C.I. 3.0-4.5). Age (R2=0.02, p <0.001), duration of illness (R2=0.01, p<0.001), and treatment regimen (R2=0.039, p<0.001) significantly explained the risk of death even though marginal. Primary Visceral leishmaniasis were 2.5 times (OR=2.5 [95% C.I. 1.4, 4.6]; p<0.002) more likely to die as compared to other categories. There are epidemic foci in North Eastern counties of Ayod, Fangak, Baliet and Canal Khorfulus. Further studies, both ecological and behavioral are required to understand the risk of exposure to VL.

EPIDEMIOLOGICAL SITUATION ON CHOLERA ACROSS THE GLOBE AND IN THE RUSSIAN FEDERATION IN 2007–2016. FORECAST FOR 2017

Analysis of epidemiological situation on cholera around the world has demonstrated downward trend in morbidity rates in 2016; annual average decline being 3.907 % (by reference to 2007). Comparative assessment of monthly incidence in 2015 and 2016 shows perennial registration of cholera cases in a number of African countries and in the Caribbean with up-rises in different seasons. Establishment of epidemic foci is on-going. Between 2007 and 2016, 1733 imported cases of cholera took place across the globe. Interstate import dominated in Asia. For forecast development, for the first time ever, risk assessment of epidemic process activation has been performed, taking into consideration emergency situations of varying origin, social and natural environments, using expert evaluation scores. Epidemic manifestations of cholera in the Russian Federation were characterized by import of the infection in 2008, 2010, 2012, and 2014; isolation of V. cholerae O1 biovar El Tor ctxA – tcpA – , ctxA + and V. cholerae O139 ctxA – and tcpA – from surface water bodies, as well as individual V. cholerae O1 biovar El Tor сtхA + tсра + . Worked out has been the algorithm for epidemiological investigation of causes and conditions of surface water body contamination with cholera vibrios. Cholera forecast worldwide and in Russia for the year 2017 remains unfavorable.

EBOLA FEVER

Problems of etiology, taxonomy and nomenclature of filoviruses, epidemiology, morbidity with a little-known by Russian medics especially dangerous exotic infectious disease - Ebola fever are examined. Significant distinguishing features of 2013 - 2015 epidemic in West Africa were detected - along with its unprecedented length, a decline did not take place as in previous outbreaks, neither causative agent virulence, nor infectivity of the infection during multiple generations from human to human. Literature data analysis allowed to assume that in the process of epidemic focus formation Ebola virus changes its properties and cyclically passes through several successive interconnected phases: an initial reservation phase in unknown ecosystems - animals, either plant, soil or water; intermediate phase of epidemic spread with primary acquisition of high virulence for humans, and then its decline; final stage of hidden circulation of causative agent that is ap-athogenic for humans. This hypothetical chain of natural phases’ transitions of Ebola virus allows to explain and link together phenomenology of this causative agent - rapid fall of virulence and infectivity for humans in foci in dynamics of epidemic outbreaks, quite a high population immunity in nosoareal of the causative agent in Africa, that contradicts the established understanding of its high lethality for humans.

HTLV-1aA introduction into Brazil and its association with the trans-Atlantic slave trade

IntroductionHuman T-lymphotropic virus (HTLV) is an endemic virus in some parts of the world, with Africa being home to most of the viral genetic diversity. In Brazil, HTLV-1 is endemic amongst Japanese and African immigrant populations. Multiple introductions of the virus in Brazil from other epidemic foci were hypothesized. The long terminal repeat (LTR) region of HTLV-1 was used to infer the origin of the virus in Brazil, using phylogenetic analysis. MethodsLTR sequences were obtained from the HTLV-1 database (http://htlv1db.bahia.fiocruz.br). Sequences were aligned and maximum-likelihood and Bayesian tree topologies were inferred. Brazilian specific clusters were identified and molecular-clock and coalescent models were used to estimate each cluster's time to the most recent common ancestor (tMRCA). ResultsThree Brazilian clusters were identified with a posterior probability ranged from 0.61 to 0.99. Molecular clock analysis of these three clusters dated back their respective tMRCAs between the year 1499 and the year 1668. Additional analysis also identified a close association between Brazilian sequences and new sequences from South Africa. ConclusionOur results support the hypothesis of a multiple introductions of HTLV-1 into Brazil, with the majority of introductions occurring in the post-Colombian period. Our results further suggest that HTLV-1 introduction into Brazil was facilitated by the trans-Atlantic slave trade from endemic areas of Africa. The close association between southern African and Brazilian sequences also suggested that greater numbers of the southern African Bantu population might also have been part of the slave trade than previously thought.

Investigation on epidemic foci of paragonimiasis in eastern part of Zhenghe County, Fujian Province

To investigate the species and hosts of Paragonimus and its infection rate in eastern part of Zhenghe County, Fujian Province, so as to determine the local foci of Paragonimus. The snails, crabs and stools of wild cats were collected for the examinations of cercariae, metacercariae and eggs of Paragonimus. The geographical and environmental conditions of the areas were also investigated. A total of 4 890 Pseudobythinella jianouensis snails and 1 035 Semisulcospira liberlina snails were examined, and the cercariae of Paragonimus were only found in P. jianouensis, with an infection rate of 0.10% (5/4 890). Bottapotamon zhengheensis sp. nov. as the second intermediate host of P. skrjabini, were examined, and the infection rate was 85.29% (29/34) and the average numbers of metacercariae per crab and per gram of crab tissues were 3.85 and 0.62, respectively. Thirty-six Sinopotamun fujianensis crabs, as the second intermediate host of P. westermani, were examined, and the infection rate was 38.89% (14/36) and the average numbers of metacercariae per crab and per gram of crab tissues were 6.43 and 0.03, respectively. The eggs of Paragonimus were detected in 1 of 2 muck specimens of wild cats. The data suggest that there is a focus of middle-to-high level of infection caused by P. westermani and P. skrjabini in the eastern part of Zhenghe County.

Effect of prevention and control system for malaria eliminating in Huai'an City

To investigate the execution and effect of the prevention and control system for malaria eliminating in Huai'an City from 2010 to 2015, so as to provide the evidence for formulating and adjusting the strategy and measures for malaria elimination. The data of network malaria reports, blood tests of feverish patients, epidemiology investigation forms of case study of malaria patients in the report system, and the investigation and disposition forms of epidemic foci were collected and analyzed statistically. From 2010 to 2015, there were 267 malaria cases in total in Huai'an City. Totally 303 016 feverish patients had blood tests, and 231 of them showed positive and the positive rate was 0.08%. The epidemiological case studies showed that all the patients were foreign imported cases except 22 local infected vivax malaria cases in 2010 and 2011. All the malaria cases were reported after diagnosis within 24 hours through the directly reported network, and the implementation rate was 100%. All the malaria cases had an epidemiological investigation within 3 days with 100% implementation rate, in which 261 (97.95%) cases were investigated within 2 days. All the cases had an epidemical investigation and disposition within 7 days with 100% implementation rate, in which 252 (94.38%) cases were completed within 5 days. The implementation rate of malaria elimination work mode has reached 100% in Huai'an City from 2010 to 2015, and there are no local infected cases in recent four years.