Bloodlines of a crisis: How arboviruses are positioning South Asia at the pandemic forefront

Dear Sir,

Contemporary epidemiology of infectious diseases has experienced profound paradigm shifts in recent decades, with arthropod-borne viruses establishing themselves as substantial threats to global public health infrastructure. These pathogens, predominantly disseminated through mosquito and tick vectors, have systematically expanded their geographical distribution and epidemiological impact, threatening potential pandemics. ^{1 -3} South Asia occupies a pivotal position, simultaneously confronting established endemic arthropod-borne pathogens and emerging novel threats. ⁴ The confluence of ecological, climatic, demographic and socio-economic determinants has combined to establish optimal conditions for arboviral emergence and proliferation, thus making the region an epicentre for future global pandemics. ⁵

Arthropod-borne viruses have emerged and re-emerged as substantial public health challenges on a nearly universal scale. ^{1 -5} The densely populated Southeast Asian region is particularly susceptible to arboviruses, including Dengue virus (DENV), Japanese encephalitis virus (JEV), West Nile virus (WNV), and Chikungunya virus (CHIKV), which are spreading in an unprecedented manner, contributing to a considerable morbidity burden.^2-4 Multiple factors, including viral genetic recombination and mutagenic processes leading to enhanced virulence strains, rapid urbanisation, and establishing conducive environments for vector–host interactions, come into play. ⁶

Arthropod-borne viruses represent a heterogeneous group of pathogens characterised by their shared transmission mechanisms. Their threat in South Asia is particularly worrying because of its dense population, constrained healthcare infrastructure, and ecological situation. ⁵ Climate change further enhances these trends. ⁵

Dengue maintains its status as the most prevalent arboviral disease, with World Health Organisation (WHO) estimates of 390 million infections annually globally. ⁷

Zika virus (ZIKV) represents the most recent concern in South Asia, gaining international renown in the 2015–2016 epidemic in the Americas with its association with severe congenital abnormalities and Guillain-Barré syndrome. ⁸ Viral circulation has been confirmed within the Southeast Asian region. ⁹ The presence of vector species, primarily Aedes aegypti and Aedes albopictus, and immunologically naive populations, establishes conditions conducive to potential ZIKV outbreaks.

JEV continues to proliferate, causing neurological sequelae, particularly among children, despite the availability of efficacious vaccines. ¹⁰

A new severe fever with thrombocytopenia syndrome virus (SFTSV), a tick-borne phlebovirus, has emerged as another significant concern, with case fatality rates ranging from 10% to 30%. ¹¹

Similarly, Tamdy virus and Karshi virus, both tick-borne arboviruses from the Nairovirus genus, have been detected in adjacent Central Asian countries and represent emerging threats to South Asia.^12,13

The COVID-19 pandemic demonstrated both vulnerability and opportunity in disease management. On the one hand, lockdown reduced transmission, but intense strain on healthcare systems diverted resources from vector control programmes, disrupted routine surveillance activity, and shifted the focus of healthcare generally. ¹⁴

The WHO plans to launch a Global Arbovirus Initiative to strengthen coordination, communication, capacity-building, research, preparedness, and response mechanisms to mitigate arboviral disease risks. ¹⁵ Its foundational pillars include risk monitoring, epidemic risk reduction, vector control strengthening, pandemic preparedness, partnership building, and innovation enhancement. ¹⁵

South Asia confronts a complex and evolving arboviral threat that demands urgent attention from national governments, regional bodies, and the international community. The convergence of factors described poses a serious threat to global health security.