Arthropod-borne viruses (arboviruses) have become significant public health problems, with the emergence and re-emergence of arboviral diseases nearly worldwide. The most populated Southeast Asia region is particularly vulnerable. The arboviral diseases such as dengue (DEN), Japanese encephalitis (JE), West Nile virus (WNV), chikungunya fever (CHIK), hemorrhagic fevers such as Crimean-Congo hemorrhagic (CCHF) fever, Kyasanur forest disease virus (KFDV), etc. are on the rise and have spread unprecedentedly, causing considerable burden of disease. The emergence/re-emergence of these diseases is associated with complex factors, such as viral recombination and mutation, leading to more virulent and adaptive strains, urbanization and human activities creating more permissive environment for vector-host interaction, and increased air travel and commerce. Climate is a major factor in determining the geographic and temporal distribution of arthropods, the characteristics of arthropod life cycles, the consequent dispersal patterns of associated arboviruses, the evolution of arboviruses; and the efficiency with which they are transmitted from arthropods to vertebrate hosts. The present and future arboviral threats must be mitigated by priority actions such as improving surveillance and outbreak response, establishing collaboration and communication intersectorally, and strengthening the prevention and control programmes along with improving biosafety aspects with regards to highly infectious nature of these arboviral diseases. Evidence from research needs to be generated and priority areas for research defined.

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Emerging and re-emerging arboviral diseases in Southeast Asia.

Ticks are distributed worldwide and can harbourand transmit a range of pathogenic microorganisms that affect livestock and humans. Most tick-borne diseases are caused by tick-borne viruses. Two major tick-borne virus zoonotic diseases, Kyasanur forest disease (KFD) and Crimean-Congo haemorrhagic fever (CCHF), are notifiable in India and are associated with highmortality rates. KFD virus was first identified in 1957 in Karnataka state; the tick Haemaphysalis spinigera is the main vector. During 2012-2013, cases were reported from previouslyunaffected areas in Karnataka, and newer areas of Kerala and Tamil Nadu states. These reports may be the result of improved active surveillance or may reflect altered virus transmission because of environmental change. CCHF is distributed in Asia, Africa and some part of Europe; Hyalomma spp. ticks are the main vectors. The existence of CCHF in India was first confirmed in 2011 in Gujaratstate. In 2013, a non-nosocomial CCHF outbreak in Amreli district, as well as positive tick, animal and human samples in various areas of Gujarat state, suggested that the virus is widespread in Gujarat state, India. The emergence of KFDand CCHF in various Indian states emphasizes the need for nationwide surveillance among animals and humans. There is a need for improved diagnostic facilities, more containment laboratories, better public awareness, and implementation ofthorough tick control in affected areas during epidemics.

Expediency of dengue illness classification: the Sri Lankan perspective Highly infectious tick-borne viral diseases: Kyasanur forest disease and Crimean-Congo haemorrhagic fever in India.

Arboviruses are transmitted between arthropod vectors and vertebrate host. Arboviral infection in mosquitoes is initiated when a mosquito feeds on a viremic host. Following ingestion of a viremic blood meal by mosquitoes, virus enters midgut along with the blood, infects and replicates in midgut epithelial cells, and then escapes to the hemocoel, from where it disseminates to various secondary organs including salivary glands. Subsequently, when mosquito bites another host, a new transmission cycle is initiated. The midgut and salivary glands act as anatomical barriers to virus infection and escape. These complex interactions between the virus and vector dictate the vector competence. Thus, vector competence reflects the success in overcoming different barriers within the vector. Along with these, other intrinsic factors like midgut microbiota and immune responses, extrinsic factors like temperature and humidity, and genetic factors like vector genotype and viral genotype have been discussed in this review. Recent advancement on novel molecular tools to study vector competence is also included. Different modes of arboviral transmission like horizontal, vertical, and venereal and how these play role in sustenance and emergence of arboviruses in nature are also discussed. These factors can be exploited to reduce the susceptibility of vectors for the viruses, so as to control arboviral diseases to certain extent.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/rmv.1941

Impact of transmission cycles and vector competence on global expansion and emergence of arboviruses.

In order to map global disease risk, a geographic database of human Crimean-Congo haemorrhagic fever virus (CCHFV) occurrence was produced by surveying peer-reviewed literature and case reports, as well as informal online sources. Here we present this database, comprising occurrence data linked to geographic point or polygon locations dating from 1953 to 2013. We fully describe all data collection, geo-positioning, database management and quality-control procedures. This is the most comprehensive database of confirmed CCHF occurrence in humans to-date, containing 1,721 geo-positioned occurrences in total.

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A global compendium of human Crimean-Congo haemorrhagic fever virus occurrence.

The biggest-ever outbreak of monkeypox disease in non-endemic countries started in May, 2022. Though no monkeypox case has been reported from India, till mid-June, 2022, yet, considering the rate of spread to the non-endemic countries, there is an urgent need of better understanding of the monkeypox virus and disease epidemiology to help clinicians, public health specialists, and policymakers to be prepared for any eventuality. This review summarises the monkeypox disease epidemiology, clinical features, therapies, vaccines and outlines the measures for preparedness and response for a possible outbreak. The disease is known to cause severe outcome in children, pregnant women, and immunocompromised hosts and this group need to be given special attention. The monkeypox disease outbreak (2022) in non-endemic countries should be used as an opportunity by India and other low and middle income countries to strengthen public health surveillance and health system capacity for outbreak and epidemic preparedness and response. 

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Monkeypox Disease Outbreak (2022): Epidemiology, Challenges, and the Way Forward

The emerging and re-emerging diseases are posing a great health risk for the last few years. One such category of diseases is viral haemorrhagic fevers (VHFs), which have emerged in the new territories, worldwide. Crimean Congo Hemorrhagic Fever (CCHF) cases, for the first time in India, were reported from Gujarat, in January 2011. The emergence of diseases not reported earlier, pose great economic and social challenge, burden health system, and create panic reaction. Nonetheless, with recent experience in control of epidemic diseases, and advances in basic scientific knowledge; the public health community is better prepared for these unexpected events. This review provides information to physicians on CCHF for managing outbreak, and identifies public health measures to prevent emergence and re-emergence of VHFs (including CCHF) in future. The authors suggest that though, there are a few challenging and unanswered questions, the public health preparedness still remains the key to control emerging and re-emerging diseases. The countries where virus activities have been reported need to be prepared accordingly.

M K Goel

Papers

Emergence of viral hemorrhagic fevers: is recent outbreak of Crimean Congo Hemorrhagic Fever in India an indication?