Arthropod- and rodent-borne viral and rickettsial diseases in the WHO South-East Asia and Western Pacific Regions: Memorandum from a WHO Meeting

Arthropod- and rodent-borne viral and rickettsial diseases continue to be one of the most important causes of morbidity and mortality in the WHO South-East Asia and Western Pacific Regions. Both epidemics and sporadic cases occur. In some years, outbreaks of dengue haemorrhagic fever and Japanese encephalitis reached alarming proportions. The significance of other arthropod- and rodent-borne viral and rickettsial diseases has still to be determined. Therefore, continuous epidemiological surveillance, diagnosis, and control of these groups of diseases remains an urgent task.     

First report of chikungunya from the Maldives

An outbreak, characterised by fever, arthralgia and myalgia, in Malé and other islands of the Maldives began in December 2006. The illness was suspected as being due to chikungunya virus based on clinical symptoms and the prevailing chikungunya epidemic in the Indian Ocean region. The Department of Public Health initiated an investigation and collected blood samples from 67 patients; 21% were IgM-positive for chikungunya and 96% were PCR-positive. Six percent were positive for dengue by enzyme immunosorbent assay and 4% had evidence of dual infection. This is the first time that chikungunya fever has been confirmed in the Maldives. A total of 11,879 suspected and confirmed cases affecting 61% of inhabited islands (attack rate ranging from 0% to 72% on individual islands) were reported by the end of the epidemic in April 2007.     

El Niño and the dynamics of vectorborne disease transmission.

The objective of the study was to investigate the relationship between reported incidence of dengue fever and El Niño southern oscillation (ENSO) in 14 island nations of the South Pacific. Using a mixed ecological study design, we calculated correlations between annual averages of the southern oscillation index (SOI), local temperature and rainfall, and dengue fever. We also calculated temporal correlations between monthly reports of dengue fever cases on different islands. There were positive correlations between SOI and dengue in 10 countries. In five of these (including all of the larger islands) there were also positive correlations between SOI and estimates of local temperature and/or rainfall. There were temporal correlations between monthly reports of dengue cases within two groups of countries. Climate changes associated with ENSO may trigger an increase in dengue fever transmission in larger, more populated islands where the disease is endemic. There was also evidence of propagation of infection from larger islands to smaller neighbors. Unlike the initiation of epidemics, this transfer between islands appears to be independent of interannual climate variations, pointing to the importance of modulating factors in dengue transmission such as population density and travel. In the future, models of the impact of climate change must attempt to account for these factors.     

Epidemiology of Chikungunya infection on Reunion Island, Mayotte, and neighboring countries

Since 2004, the frequency of chikungunya virus infections has been increasing in Africa, Indian Ocean islands, and Asia. The epidemic began on the Kenyan coast, and reached the Comoros at the end of 2004 before spreading to the South-western Indian Ocean islands (SWIOI) in 2005 and especially in 2006. The epidemic then spread to Asia where epidemic foci are still active today. This increase also affected temperate zone countries where imported cases were reported, and indigenous transmission was reported in Italy in 2007, and in France (Var) in 2010. This review provides an update on the knowledge gained from monitoring chikungunya infections in SWIOI. Despite significant differences in design and performance, the implementation of surveillance systems has allowed describing the evolution of epidemic waves in the affected areas. Synchronous epidemic waves were observed in SWIOI, despite the differences between the preventive measures locally implemented. Between 2005 and 2007, all SWIOI were in inter-epidemic situation, except for Madagascar where a persistent virus circulation in an endemic-epidemic pattern was observed. In 2009, and in 2010, two moderate indigenous outbreaks were identified on the Reunion Island by the inter-epidemic surveillance system. Strains analyses demonstrated a reintroduction of the virus from Madagascar. These limited outbreaks should be a reminder of the vulnerability of SWIOI to arbovirosis, since the entomological indexes for competent vectors are high and the virus keeps on circulating more or less actively in the area.     

Resurgence of chikungunya

Chikungunya, an arboviral disease transmitted by Aedes mosquitoes, has recently increased dramatically in incidence and geographic extent. Large outbreaks have affected islands of the Indian Ocean, India and other parts of South and Southeast Asia, Africa and most recently Italy. International travellers have disseminated new strains of the virus, some into regions from which chikungunya has hitherto been absent. In parallel, over the past 30 years international trade has resulted in the spread of A. albopictus from its original range in Asia, to all continents but Antarctica, thereby extending the geographic area over which transmission can occur.     

An outbreak of type 2 dengue fever in the Seychelles, probably transmitted by Aedes albopictus (Skuse)

Between December 1976 and September 1977 the Seychelles group of islands in the Indian Ocean was struck by an extensive epidemic of dengue fever. The peak of the epidemic was in the last week of February. Type 2 dengue virus was isolated from patients and mosquitos. Aedes albopictus was the sole vector. The clinical picture was that of classical dengue. Haemorrhagic fever and the shock syndrome were not observed.     

Novel chikungunya virus variant in travelers returning from Indian Ocean islands

Chikungunya virus (CHIKV) emerged in Indian Ocean islands in 2005 and is causing an ongoing outbreak that involves >260,000 patients, including travelers returning home from these islands. We investigated cases in 4 patients returning from Mayotte and Reunion Islands with CHIKV infection and a nurse infected in metropolitan France after direct contact with the blood of a traveler. Four patients had tenosynovitis and pain at wrist pressure, and 1 had life-threatening manifestations. Four CHIKV strains were isolated, including 1 from the patient with the autochthonous case. The complete genomic sequence identified a new CHIKV variant emerging from the East/ central African evolutionary lineage. Aedes albopictus, the implicated vector of CHIKV in Indian Ocean islands, has dispersed worldwide in recent decades. High viral loads in patients returning from Indian Ocean islands to countries where Ae. albopictus is prevalent may be a source of epidemics.     

Clinical Manifestations and Trend of Dengue Cases Admitted in a Tertiary Care Hospital, Udupi District, Karnataka

Background:

India is one of the seven identified countries in the South-East Asia region regularly reporting dengue fever (DF)/dengue hemorrhagic fever (DHF) outbreaks and may soon transform into a major niche for dengue infection in the future with more and more new areas being struck by dengue epidemics

Objective:

To study the clinical manifestations, trend and outcome of all confirmed dengue cases admitted in a tertiary care hospital.

Study Design:

Record-based study conducted in a coastal district of Karnataka. Required data from all the laboratory confirmed cases from 2002 to 2008 were collected from Medical Records Department (MRD) and analyzed using SPSS 13.5 version.

Results:

Study included 466 patients. Majority were males, 301(64.6%) and in the and in the age group of 15-44 years, 267 (57.5%). Maximum number of cases were seen in 2007, 219 (47%) and in the month of September, 89 (19.1%). The most common presentation was fever 462 (99.1%), followed by myalgia 301 (64.6%), vomiting 222 (47.6%), headache 222 (47.6%) and abdominal pain 175 (37.6%). The most common hemorrhagic manifestation was petechiae 84 (67.2%). 391 (83.9%) cases presented with dengue fever, 41 (8.8%) dengue hemorrhagic fever, and 34 (7.3%) with dengue shock syndrome. Out of 66 (14.1%) patients who developed clinical complications, 22 (33.3%) had ARDS and 20 (30.3%) had pleural effusion. Deaths reported were 11(2.4%).

Conclusion:

Community awareness, early diagnosis and management and vector control measures need to be strengthened, during peri-monsoon period, in order to curb the increasing number of dengue cases.     

Dengue fever in the Indian Subcontinent: an overview

The Indian Subcontinent has emerged as a scene of many mosquito-borne infectious diseases, including malaria and dengue fever. After the 1990s, the rate of malaria declined owing largely to preventive measures, but at the same time dengue fever (DF) and dengue hemorrhagic fever (DHF) were increasing in the region. Outbreaks were recorded in all countries of the Indian Subcontinent with India, Pakistan, Bangladesh and Sri Lanka on the forefront and suffering from the largest number of cases and deaths. We discuss annual cases of DF/DHF in these four countries and possible factors involved in DF outbreaks. We also discuss prevalent serotypes in this region where data suggest the emergence of DEN2 and DEN3 as the most dominant and lethal serotypes. Climate is an important factor influencing DF outbreaks, and rainfall, temperature and humidity play a pivotal role in DF outbreaks. Finally the economic impact of DF/DHF cases is discussed showing that direct and indirect economic loss due to DF/DHF reaches millions of USD each year.     

Temporal-spatial risk model to identify areas at high-risk for occurrence of dengue fever

OBJECTIVE: To apply the temporal-spatial model to assess high-risk areas for the occurrence of dengue fever. METHODS: A total of 11,989 confirmed, autochthonous dengue fever cases, geocoded by address in the city of S?o José do Rio Preto (Southeastern Brazil), between September of 2001 and August of 2006, were included in the study. Frequency, duration and intensity indices were used to assess the severity and magnitude of transmission. The local indicator of spatial association was adopted to identify significant spatial clusters (p-value<0.05). The values of the three indices were considered high in a spatial unit when their standard values were positive and the respective local indicator of spatial association values were significant. RESULTS: Of all the geocoded dengue fever cases, 38.1% occurred in the urban spatial units, classified as highest-risk: 19.4% in 2001-2002, 13.9% in 2002-2003, 2.8% in 2003-2004, 16.7% in 2004-2005, and 21.3% in 2005-2006. The utilization of three risk measures enabled to identify higher-risk areas for the occurrence of dengue fever, concentrated in the city's northern region. Even though case notification data are subject to bias, this information is available in the health services and can lead to important conclusions, recommendations and hypotheses. CONCLUSIONS: The non-complex, notification-based procedures adopted in the study could be routinely used by services that are responsible for dengue fever surveillance and control to identify high-risk areas.     

Emergence of dengue virus serotype 3 on Mayotte Island, Indian Ocean

A serosurvey carried out in 2006 in Mayotte, a French overseas collectivity in the Indian Ocean, confirmed previous circulation of dengue virus (DENV) on the island, but since the set up of a laboratory-based surveillance of dengue-like illness in 2007, no case of DENV has been confirmed. In response to an outbreak of DENV-3 on Comoros Islands in March 2010 surveillance of dengue-like illness in Mayotte was enhanced. By September 15, 76 confirmed and 31 probable cases of DENV have been identified in Mayotte. In urban and periurban settings on the island, Aedes albopictus is the predominant Aedes species, but Ae. aegyptii remains the most common species in rural areas. Given the epidemic potential of dengue virus in Mayotte, adequate monitoring including early detection of cases, timely investigation and sustained mosquito control actions remain essential.     

Phylogenetic analysis of dengue virus types 1 and 3 isolated in Jakarta,Indonesia in 1988

Dengue viruses are mosquito-borne viruses that cause dengue fever and dengue hemorrhagic fever, both of which are globally important diseases. These viruses have evolved in a transmission cycle between human hosts and mosquito vectors in various tropical and subtropical environments. We previously isolated three strains of dengue type 1 virus (DENV1) and 14 strains of dengue type 3 virus (DENV3) during an outbreak of dengue fever and dengue hemorrhagic fever in Jakarta, Indonesia in 1988. Here, we compared the nucleotide sequences of the entire envelope protein-coding region among these strains. The isolates were 97.6–100% identical for DENV1 and 98.8–100% identical for DENV3. All DENV1 isolates were included in two different clades of genotype IV and all DENV3 isolates were included in a single clade of genotype I. For DENV1, three Yap Island strains isolated in 2004 were the only strains closely related to the present isolates; the recently circulated Indonesian strains were in different clades. Molecular clock analyses estimated that ancestors of the genotype IV strains of DENV1 have been indigenous in Indonesia since 1948. We predict that they diverged frequently around 1967 and that their offspring distributed to Southeast Asia, the Western Pacific, and Africa. For DENV3, the clade containing all the present isolates also contained strains isolated from other Indonesian regions and other countries including Malaysia, Singapore, China, and East Timor from 1985–2010. Molecular clock analyses estimated that the common ancestor of the genotype I strains of DENV3 emerged in Indonesia around 1967 and diverged frequently until 1980, and that their offspring distributed mainly in Southeast Asia. The first dengue outbreak in 1968 and subsequent outbreaks in Indonesia might have influenced the divergence and distribution of the DENV1 genotype IV strains and the DENV3 genotype I strains in many countries.     

Dengue surveillance in Florida, 1997-98

Recent dengue outbreaks in the Caribbean and Central and South America and the presence of competent mosquito vectors increase the likelihood of future autochthonous transmission in Florida. During April 1997 to March 1998, a laboratory-based active surveillance program detected 18 cases of dengue involving all four dengue serotypes. All patients reported recent travel to countries with indigenous dengue transmission. These results demonstrate that dengue infections are imported into Florida at a much higher rate than reflected by previous passive surveillance; therefore, the risk for local dengue transmission may be increasing.     

北京市2006-2010年登革热发病情况及其传播媒介的调查

目的 分析北京市近5年登革热病例流行病学特征,并结合北京市病媒生物监测数据,分析北京市出现登革热暴发的风险.方法 采用SPSS软件分析北京市登革热病例的流行病学特征;采用CO2诱蚊灯法调查北京市蚊类种群构成及其密度.结果 2006-2010年北京市累计报告23例登革热病例,均为输入性病例,其中25～59岁病例占95.65％(22/23),男女性别之比为4.75∶1.病例的职业分布以干部职员为主(69.57％,16/23).与2007年相比,2010年白纹伊蚊的构成比增加了25.71倍,密度增加了6.00倍.结论 近几年北京市亚优势蚊种白纹伊蚊密度逐年增加,应继续做好蚊类监测,为登革热防控提供科学依据.     

Dengue: a newly emerging viral infection in Andaman and Nicobar Islands, India

Prior to 2009 dengue fever had not been reported in the Andaman and Nicobar archipelago. In 2009, a few patients with dengue fever-like illness were reported, some of whom tested positive for dengue antibodies. In 2010, 516 suspected cases were reported, including some with dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS); 80 (15·5%) were positive for dengue antibodies. DENV RNA was detected in five patients and PCR-based typing showed that three of these belonged to serotype 1 and two to serotype 2. This was confirmed by sequence typing. Two clones of dengue virus, one belonging to serotype 1 and the other to serotype 2 appeared to be circulating in Andaman. Emergence of severe diseases such as DHF and DSS might be due to recent introduction of a more virulent strain or because of the enhancing effect of sub-neutralizing levels of antibodies developed due to prior infections. There is a need to revise the vector-borne disease surveillance system in the islands.     

A survey of the distribution and relative prevalence of Aedes aegypti in Sabah, Brunei, and Sarawak

Although dengue haemorrhagic fever is widely established in South-East Asia, no cases have been reported from Borneo. In order to help to assess whether the infection could become established in Borneo, a survey was made, using the single-larva collection method, of the distribution and prevalence of the principal vector, Aedes aegypti, in Sabah and in a few towns and villages of Brunei and Sarawak. In addition, the prevalence of Ae. aegypti was compared with that of certain other species of Aedes.     

Autochthonous Melioidosis in Humans,Madagascar, 2012 and 2013

Melioidosis is an often fatal infectious disease affecting humans and animals in the tropics. Only sporadic cases have been reported from Africa and the Indian Ocean region. We describe 2 confirmed autochthonous cases of human melioidosis in Madagascar, both from novel genotypes of Burkholderia pseudomallei.     

2015－2018年我国登革热暴发流行病学特征分析

目的 分析2015-2018年我国登革热暴发流行病学特征,为制定登革热防控策略提供参考。方法 收集和分析中国疾病预防控制信息系统、突发公共卫生事件报告管理信息系统及病媒生物监测系统上报的登革热发病及媒介监测数据,描述登革热暴发流行病学特征。应用Excel 2010和SPSS 20.0软件整理数据和分析,采用ArcGIS 10.5软件绘制地图。结果 2015-2018年全国累计报告登革热暴发111起,共涉及病例12 490例,占全国病例总数的73.7%。暴发集中在广东（77起）、云南（14起）、浙江（8起）和福建（8起）4省份,共累及85个县（区）。暴发集中在5-11月,病例≤ 10例的小规模暴发多于30 d内终止（28/34,82.4%）,较大规模暴发多持续数月,于10-11月终止。登革病毒1型和2型为我国登革热暴发的主要流行株。疫情主要发生在人口密度大、卫生环境差的区域。主要暴发省份病例的年龄和职业构成差异有统计学意义。结论 我国登革热暴发呈地域扩散、甚至向高纬度扩散态势,不同省份暴发特征各异,总体分为口岸型、乡村型和城市型,各省份应针对性调整防控策略。     

Comparison of the Epidemiological Aspects of Imported Dengue Cases between Korea and Japan, 2006–2010

To compare the epidemiological characteristics of dengue cases imported by travelers or immigration in both Korea and Japan, we determined dengue incidence and related risk factors. During 2006–2010, 367 and 589 imported dengue cases were reported in Korea and Japan, respectively. In Korea, the presumptive origins for the dengue infections were Southeast Asia (82.6%), Southern Asia (13.9%), Eastern Asia (1.1%), South America (0.3%), Central America (0.3%), Africa (0.3%), and other countries (1.6%). In Japan, the origins of the infections were Southeast Asia (69.8%), Southern Asia (20.0%), Eastern Asia (1.7%), South America (2.5%), Central America (1.2%), Africa (1.2%), Oceania (2.4%), and other countries (1.2%). In both countries, more dengue cases were reported for men than for women (p < 0.01), and those aged 20–30 years accounted for > 60% of the total cases. The frequency of imported cases in summer and autumn (∼70% of total cases) was similar in both countries. This study demonstrates that there is a similar pattern of imported dengue cases in Korea and Japan. Therefore, there is a risk of an autochthonous dengue outbreak in Korea, as indicated by the recent outbreak in Japan in 2014.