Background: Dengue is a growing problem both in its geographical spread and in its intensity, and yet current global distribution remains highly uncertain. Challenges in diagnosis and diagnostic methods as well as highly variable national health systems mean no single data source can reliably estimate the distribution of this disease. As such, there is a lack of agreement on national dengue status among international health organisations. Here we bring together all available information on dengue occurrence using a novel approach to produce an evidence consensus map of the disease range that highlights nations with an uncertain dengue status. Methods/Principal Findings: A baseline methodology was used to assess a range of evidence for each country. In regions where dengue status was uncertain, additional evidence types were included to either clarify dengue status or confirm that it is unknown at this time. An algorithm was developed that assesses evidence quality and consistency, giving each country an evidence consensus score. Using this approach, we were able to generate a contemporary global map of national-level dengue status that assigns a relative measure of certainty and identifies gaps in the available evidence. Conclusion: The map produced here provides a list of 128 countries for which there is good evidence of dengue occurrence, including 36 countries that have previously been classified as dengue-free by the World Health Organization and/or the US Centers for Disease Control. It also identifies disease surveillance needs, which we list in full. The disease extents and limits determined here using evidence consensus, marks the beginning of a five-year study to advance the mapping of dengue virus transmission and disease risk. Completion of this first step has allowed us to produce a preliminary estimate of population at risk with an upper bound of 3.97 billion people. This figure will be refined in future work.

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Refining the global spatial limits of dengue virus transmission by evidence-based consensus

Chikungunya is an arboviral disease transmitted by aedes mosquitoes. The virus was fi rst isolated in 1953 in Tanzania. Chikungunya virus is a member of the genus Alphavirus and the family Togaviridae. The disease typically consists of an acute illness characterised by fever, rash, and incapacitating arthralgia. The word chikungunya, used for both the virus and the disease, means “to walk bent over” in some east African languages, and refers to the eff ect of the joint pains that characterise this dengue-like infection. Chikungunya is a specifi cally tropical disease, but it is geographically restricted and outbreaks are relatively uncommon. It is only occasionally observed in travellers and military personnel. More than 266 000 people have been infected during the ongoing outbreak in Reunion, in which Aedes albopictus is the presumed vector. In the ongoing Indian outbreak, in which Aedes aegypti is the presumed vector, 1 400 000 cases of chikungunya were reported during 2006. The reasons for the re-emergence of chikungunya on the Indian subcontinent, and for its unprecedented incidence rate in the Indian Ocean region, are unclear. Plausible explanations include increased tourism, chikungunya virus introduction into a naive population, and viral mutation.

http://antimicrobe.org/h04c.files/history/LancetID_Pialouxetal_Chikugunya,%20an%20Epidemic%20Arbovirus_2007.pdf

Chikungunya, an epidemic arbovirosis.

Arthropod-borne viruses (arboviruses) are the causative agents of some of the most important emerging infectious diseases and are responsible for significant global public health problems (Gubler, 2001). Of these viruses, the genus Alphavirus belongs in the family Togaviridae, and the species in this genus cause diseases ranging from mild febrile illness to severe polyarthritis to encephalitis. One alphavirus, chikungunya virus (CHIKV), caused recent outbreaks associated with severe morbidity. Traditionally, CHIKV causes a febrile illness similar to that seen in dengue virus infections. The hallmark feature of CHIKV disease is a debilitating and prolonged arthralgic syndrome that primarily affects the peripheral small joints. While the acute febrile phase of the illness normally resolves within a few days, the pain associated with CHIKV infection of the joints typically persists for weeks or months causing serious economic and social impact on both the individual and the affected communities. During the 2005–2007 explosive epidemics on the Indian Ocean islands and in India, anecdotal cases of CHIKV-associated deaths, encephalitis and neonatal infections were reported. Here, we review outbreaks of CHIKV disease and present a comprehensive analysis and comparison of clinical presentation, virus– vector associations and viral genetics to assess the possibility of further expansion and re-emergence of CHIKV illness.

Changing patterns of chikungunya virus: re-emergence of a zoonotic arbovirus

Background Chikungunya is a reemerging disease. In 2005-2006, a severe outbreak occurred on Reunion Island in the southwestern part of the Indian Ocean. Other islands in this area were affected during the same period. Methods Adult patients with acute chikungunya (defined as onset of fever and/or polyarthralgia in the 5 days preceding consultation) and laboratory-confirmed chikungunya who were referred to Groupe Hospitalier Sud Reunion during the period from March 2005 through April 2006 were included in this retrospective study. Their clinical and laboratory features are reported. Results Laboratory-confirmed acute chikungunya was documented in 157 patients. The mean age of patients was 57.9 years, and the ratio of male to female patients was 1.24 : 1. Sixty percent of patients had at least 1 comorbidity. Ninety-seven patients (61.8%) were hospitalized, and 60 (38.2%) were treated as outpatients. Five fatalities were reported. One hundred fifty-one patients (96.1%) experienced polyarthralgia, and 129 (89%) experienced fever. Gastrointestinal symptoms were reported by 74 patients (47.1%), and skin rash was reported by 63 (40.1%). Hemorrhagic signs were rare. Lymphopenia and hypocalcemia were the prominent laboratory findings. Severe thrombocytopenia was rarely observed. Conclusions Chikungunya virus can be responsible for explosive outbreaks of disease. Polyarthralgia and fever are the 2 main clinical features. In this era of travel and globalization, chikungunya should be considered in the differential diagnosis of febrile polyarthralgia with an abrupt onset.

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Outbreak of Chikungunya on Reunion Island: Early Clinical and Laboratory Features in 157 Adult Patients

Background An outbreak of chikungunya virus infection occurred on Reunion Island during the period 2005-2006. Persistent arthralgia after chikungunya virus infection has been reported, but few studies have treated this aspect of the disease. Methods Adult patients with laboratory-confirmed acute chikungunya virus infection who were referred to Groupe Hospitalier Sud Reunion during the period 2005-2006 were asked to participate in the study. Patients were assessed a mean of 18 months after acute disease occurred. Assessment consisted of answering questions on a standard form, undergoing a medical examination, and being tested for the presence of IgM antibodies to chikungunya virus. Results Eighty-eight patients (mean age, 58.3 years; male-to-female ratio, 1.1:1.0) were included in this study. Fifty-eight patients (65.9%) had been hospitalized for acute chikungunya virus infection, and a history of arthralgia before chikungunya virus infection was reported by 39 patients (44%). Fifty-six patients (63.6%) reported persistent arthralgia related to chikungunya virus infection, and in almost one-half of the patients, the joint pain had a negative impact on everyday activities. Arthralgia was polyarticular in all cases, and pain was continuous in 31 patients (55.4%). Overall, 35 patients (39.7%) had test results positive for IgM antibodies to chikungunya virus. Conclusions Persistent and disabling arthralgia was a frequent concern in this cohort of patients who had experienced severe chikungunya virus infection approximately 18 months earlier. Further studies are needed to evaluate the prevalence of persistent arthralgia in the general population to determine the real burden of the disease.

Persistent Arthralgia Associated with Chikungunya Virus: A Study of 88 Adult Patients on Reunion Island

A serological survey for antibody to dengue and chikungunya was carried out in all 14 divisions and states and 2 border towns in Burma during 1973-74. Dengue HI antibody prevalence rate of less than 10% was observed in Arakan and Shan States, 10 to 30% in the Irrawaddy, Pegu, Mandalay Divisions and Kachin, Mon and Karen States, 31 to 60% in Sagaing Division, and over 60% in Rangoon, Magwe and Tenasserim Divisions. Similarly, chikungunya HI antibody prevalence rate of less than 10% was observed in Arakan State, 10 to 30% in the Irrawaddy, Pegu, Mandalay and Sagaing Divisions and Kachin State, 31 to 60% in Rangoon Division and Mon State. Both dengue and chikungunya antibodies were detected where Aedes aegypti mosquitoes were prevalent but the antibody prevalent rates were not directly proportional to the premises index. No HI antibody to dengue nor chikungunya was detected in Aedes aegypti free hilly areas, Chin and Kayah States, but was detected in the Shan State, Dengue and chikungunya infections were observed both in rural and urban populations. Dengue and chikungunya infections affected all socioeconomic classes in Rangoon equally but in Mandalay high socioeconomic class was nearly 3 times less affected than lower socioeconomic class. The infrequencies of dengue and chikungunya infections were observed to be 2 to 3 times higher in residents of Rangoon City than those of other towns. In Rangoon the antibody prevalence rates to dengue increased progressively with age while in other towns no appreciable increase in rates with age was observed. Both sexes were equally affected. This study provides strong circumstantial evidence that dengue and chikungunya viruses are highly and widely distributed throughout Burma, and that new outbreaks of haemorrhagic fever could occur in previously free areas following introduction of dengue viruses into populations previously exposed to one type of dengue.

Thein S

Papers

Epidemiological features of dengue and chikungunya infections in Burma.