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.

/pdf/refining-the-global-spatial-limits-of-dengue-virus-f8emry0wk5.pdf

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.

Chikungunya fever is an acute febrile illness associated with severe, often debilitating polyarthralgias. The disease is caused by Chikungunya virus (CHIKV), an arthropod-borne virus that is transmitted to humans primarily via the bite of an infected mosquito. Since a re-emergence of CHIKV in 2004, the virus has spread into novel locations, such as Europe, and has led to millions of cases of disease throughout countries in and around the Indian Ocean. The risk of importation of CHIKV into new areas is ever present because of the high attack rates associated with the recurring epidemics, the high levels of viremia in infected humans, and the worldwide distribution of the vectors responsible for transmitting CHIKV. In this review, we will characterize the epidemiology and global expansion of CHIKV, describe the clinical features and laboratory testing for the disease, and discuss priorities for further studies needed for effective disease control and prevention.

Chikungunya Fever: An Epidemiological Review of a Re-Emerging Infectious Disease

Phlebotomine sandflies transmit pathogens that affect humans and animals worldwide. We review the roles of phlebotomines in the spreading of leishmaniases, sandfly fever, summer meningitis, vesicular stomatitis, Chandipura virus encephalitis and Carrion's disease. Among over 800 species of sandfly recorded, 98 are proven or suspected vectors of human leishmaniases; these include 42 Phlebotomus species in the Old World and 56 Lutzomyia species in the New World (all: Diptera: Psychodidae). Based on incrimination criteria, we provide an updated list of proven or suspected vector species by endemic country where data are available. Increases in sandfly diffusion and density resulting from increases in breeding sites and blood sources, and the interruption of vector control activities contribute to the spreading of leishmaniasis in the settings of human migration, deforestation, urbanization and conflict. In addition, climatic changes can be expected to affect the density and dispersion of sandflies. Phlebovirus infections and diseases are present in large areas of the Old World, especially in the Mediterranean subregion, in which virus diversity has proven to be higher than initially suspected. Vesiculovirus diseases are important to livestock and humans in the southeastern U.S.A. and Latin America, and represent emerging human threats in parts of India. Carrion's disease, formerly restricted to regions of elevated altitude in Peru, Ecuador and Colombia, has shown recent expansion to non-endemic areas of the Amazon basin.

https://onlinelibrary.wiley.com/doi/epdf/10.1111/j.1365-2915.2012.01034.x

Phlebotomine sandflies and the spreading of leishmaniases and other diseases of public health concern

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(11)60281-X.pdf

Chikungunya: a re-emerging virus

An outbreak of dengue-like disease was observed in Luanda, Angola, at the end of 1970 and beginning of 1971. Chikungunya virus was isolated from the blood of a patient with typical symptoms of dengue and from a pool of Aedes aegypti mosquitos. A survey for antibodies to arboviruses in the sera of persons living in Luanda showed that the Chikungunya virus was indeed responsible for the outbreak. The fact that this outbreak immediately preceded and continued concurrently with a yellow fever epidemic in Luanda shows that two arboviruses from different antigenic groups may circulate simultaneously in the same ecological area.

Arbovirus studies in Luanda, Angola. 2. Virological and serological studies during an outbreak of dengue-like disease caused by the Chikungunya virus.

A serologic survey for antibodies to arboviruses in serum from domestic animals, cattle and sheep, from the south of Portugal was done with the hemagglutination-inhibition (HI) test. The following viruses were used as antigens: Sindbis, chikungunya, West Nile, Central European tick-borne encephalitis (TBE), Israel turkey meningoencephalitis (ITME), Batai, and Ťahyňa. Of the bovine serum, 16% had HI antibodies to West Nile virus, with titers ranging from 1:20 to 1:5,120; and these specimens also reacted with the TBE antigen (5.1%) and with the ITME antigen (8.2%), but this reactivity was probably due to serologic overlap. None of the serum specimens after acetone treatment gave positive tests with the Sindbis or with the chikungunya antigens. The percentage of serum positive to the Batai and to the Ťahyňa antigens was 2% and 3% respectively.

Survey for antibodies to arboviruses in serum of animals from southern Portugal.

Prototype Thogoto virus from Kenya and Thogoto virus isolates from Portugal, Italy, Nigeria, Central African Republic, Cameroon, and Iran were cross-tested by hemagglutination inhibition and serum dilution plaque reduction neutralization. Considering the broad geographic distribution of these strains, the antigenic differences seen appear to be essentially minor. This uniformity suggests that the distribution of Thogoto virus is due to repeated introduction of virus from common sources and that such introduction may depend on the movement of tick-infested domestic animals.

Antigenic uniformity of topotype strains of Thogoto virus from Africa, Europe, and Asia.

A survey for antibodies to arboviruses in human sera was carried out to study the prevalence of infection with these viruses in the human population. Sera were obtained from 1,649 persons living in the country. The HI test showed that 3·3% of the population studied had antibodies to arboviruses, especially to group B. Neutralization tests done with some sera confirmed this information.

Serological survey for antibodies to arboviruses in the human population of Portugal

A yellow fever epidemic broke out in Luanda, Angola, in January 1971 and was halted in less than 3 months by prompt mass vaccination and intensive antimosquito measures. Nine strains of yellow fever virus were isolated from hospitalized cases, but attempts to isolate the virus from Aedes aegypti mosquitos failed. A serological survey for antibodies to arboviruses in 589 sera from unvaccinated persons showed that two arboviruses were circulating in the epidemic area: the yellow fever virus and the Chikungunya virus responsible for an outbreak of dengue-like disease that occurred shortly before the yellow fever epidemic.

Armindo R. Filipe

Papers

Arbovirus studies in Luanda, Angola. 2. Virological and serological studies during an outbreak of dengue-like disease caused by the Chikungunya virus.

Survey for antibodies to arboviruses in serum of animals from southern Portugal.

Antigenic uniformity of topotype strains of Thogoto virus from Africa, Europe, and Asia.

Serological survey for antibodies to arboviruses in the human population of Portugal

Arbovirus studies in Luanda, Angola. 1. Virological and serological studies during a yellow fever epidemic.