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Mosquito-borne viruses, or arboviruses, have been part of the infectious disease landscape for centuries, and are often, but not exclusively, endemic to equatorial and subtropical regions of the world. The past two decades saw the re-emergence of arthritogenic alphaviruses, a genus of arboviruses that includes several members that cause severe arthritic disease. Recent outbreaks further highlight the substantial public health burden caused by these viruses. Arthritogenic alphaviruses are often reported in the context of focused outbreaks in specific regions (eg, Caribbean, southeast Asia, and Indian Ocean) and cause debilitating acute disease that can extend to chronic manifestations for years after infection. These viruses are classified among several antigenic complexes, span a range of hosts and mosquito vectors, and can be distributed along specific geographical locations. In this Review, we highlight key features of alphaviruses that are known to cause arthritic disease in humans and outline the present findings pertaining to classification, immunogenicity, pathogenesis, and experimental approaches aimed at limiting disease manifestations. Although the most prominent alphavirus outbreaks in the past 15 years featured chikungunya virus, and a large body of work has been dedicated to understanding chikungunya disease mechanisms, this Review will instead focus on other arthritogenic alphaviruses that have been identified globally and provide a comprehensive appraisal of present and future research directions.

For decades, arboviral diseases were considered to be only minor contributors to global mortality and disability. As a result, low priority was given to arbovirus research investment and related public health infrastructure. The past five decades, however, have seen an unprecedented emergence of epidemic arboviral diseases (notably dengue, chikungunya, yellow fever, and Zika virus disease) resulting from the triad of the modern world: urbanisation, globalisation, and international mobility. The public health emergency of Zika virus, and the threat of global spread of yellow fever, combined with the resurgence of dengue and chikungunya, constitute a wake-up call for governments, academia, funders, and WHO to strengthen programmes and enhance research in aedes-transmitted diseases. The common features of these diseases should stimulate similar research themes for diagnostics, vaccines, biological targets and immune responses, environmental determinants, and vector control measures. Combining interventions known to be effective against multiple arboviral diseases will offer the most cost-effective and sustainable strategy for disease reduction. New global alliances are needed to enable the combination of efforts and resources for more effective and timely solutions.

Oropouche fever is an emerging zoonotic disease caused by Oropouche virus (OROV), an arthropod transmitted Orthobunyavirus circulating in South and Central America. During the last 60 years, more than 30 epidemics and over half a million clinical cases attributed to OROV infection have been reported in Brazil, Peru, Panama, Trinidad and Tobago. OROV fever is considered the second most frequent arboviral febrile disease in Brazil after dengue fever. OROV is transmitted through both urban and sylvatic transmission cycles, with the primary vector in the urban cycle being the anthropophilic biting midge Culicoides paraensis. Currently, there is no evidence of direct human-to-human OROV transmission. OROV fever is usually either undiagnosed due to its mild, self-limited manifestations or misdiagnosed because its clinical characteristics are similar to dengue, chikungunya, Zika and yellow fever, including malaria as well. At present, there is no specific antiviral treatment, and in the absence of a vaccine for effective prophylaxis of human populations in endemic areas, the disease prevention relies solely on vector control strategies and personal protection measures. OROV fever is considered to have the potential to spread across the American continent and under favorable climatic conditions may expand its geographic distribution to other continents. In view of OROV’s emergence, increased interest for formerly neglected tropical diseases and within the One Health concept, the existing knowledge and gaps of knowledge on OROV fever are reviewed.

Arboviruses represent a major cause of illness in Africa and have the potential to trigger widespread epidemics. We present data on arbovirus epidemics in Africa in 2023 and demonstrate the need for global public health authorities to intensify efforts in the surveillance and control of arbovirus diseases. Data were collected from the World Health Organization Weekly Bulletin on Outbreaks and Other Emergencies, Africa Centers for Disease Control and Prevention Weekly Event Based Surveillance Report, and other online sources. In 2023, a total of 7 arboviruses were responsible for 29 outbreaks across 25 countries in Africa, 22 of which occurred in West Africa; the outbreaks resulted in 19,569 confirmed cases and 820 deaths. Arbovirus epidemics in Africa pose a threat not only to public health within the continent but also globally, underscoring the urgent need for substantial investment in arbovirus surveillance, research, and preparedness capacities in Africa to prevent and respond to health crises effectively.

Arboviruses are viruses that are transmitted by arthropods such as mosquitoes, ticks, and flies, and most of them are RNA viruses. Vector-borne transmission occurs when an infected arthropod bites a vertebrate host, allowing the virus to enter the bloodstream and initiate infection. Arboviruses are known to cause significant morbidity and mortality in mammals, and at least a hundred of them have been identified as human pathogens. In this review, we provide an updated overview of four prominent arboviruses that are present in Southeast Asia (SEA): dengue virus (DENV), Japanese encephalitis virus (JEV), Zika virus (ZIKV), and chikungunya virus (CHIKV). The epidemiology and pathogenesis of these viruses and the currently used methods for diagnosis, prevention, and treatment of arbovirus infections are discussed in detail. Finally, we summarise the concerns and future considerations for combating these dangerous pathogens.

Arboviruses have expanded into new regions in Europe, yet data indicate gaps in disease notifications and a risk of further spread. We aimed to report on prevalence, clinical management, and outcomes of endemic arbovirus infections in southeast Europe. In this prospective observational study (MERMAIDS-ARBO), we enrolled adults (age ≥18 years) hospitalised with an arbovirus-compatible disease syndrome within 21 days of symptom onset across 21 hospitals in seven countries in southeast Europe over four arbovirus seasons (May 1–Oct 31, during 2016–19). We obtained data from case report forms completed by site investigators on admission and discharge. Participants were excluded if they had non-infectious CNS disorders, symptoms of another confirmed cause, an identified focal source of infection, or symptoms caused by recurrence of a pre-existing condition. The primary outcome was the proportion of participants with confirmed or probable acute infections with West Nile virus (WNV), tick-borne encephalitis virus (TBEV), Crimean–Congo haemorrhagic fever virus (CCHFV), or Toscana virus (TOSV), per reference laboratory criteria. Secondary outcomes were the proportions of patients treated with antivirals, antibiotics, or corticosteroids; the proportion of patients requiring intensive care; hospital length of stay; and mortality. Of 2896 adults screened for eligibility, 929 were recruited and 913 met protocol-defined eligibility criteria (median age 43·1 years [IQR 29·5–59·7]; 550 [60%] men, 361 [40%] women, and two [<1%] with missing data). 530 (58%) participants presented with suspected meningitis, encephalitis, or both, and 318 (35%) with fever plus myalgia, fever plus arthralgia, or both. 820 (90%) reported no international travel within 21 days before symptom onset. 727 (80%) were administered antibiotics, 379 (42%) corticosteroids, and 222 (24%) antivirals. The median length of hospital stay was 9 days (IQR 6–14), and 113 (12%) required intensive care. Of 847 participants with a reference laboratory sample who met full eligibility criteria for analysis, 110 (13%) were diagnosed with 114 confirmed or probable acute arbovirus infections (four had coinfections or cross-reactivity): one (<1%) with CCHFV, 16 (2%) with TBEV, 44 (5%) with TOSV, and 53 (6%) with WNV. There was one death (<1%) of an individual with WNV. Of the 110 participants, 49 (45%) had a local clinician-attributed arbovirus discharge diagnosis. Our data highlight the need to strengthen arbovirus surveillance systems for the early detection of emerging and re-emerging outbreaks, including investments to increase awareness of arbovirus infections among clinicians, to improve access to specialist diagnostics, and to develop effective and accessible vaccines and treatments to protect populations and health systems in southeast Europe. European Commission and Versatile Emerging infectious disease Observatory. For the Greek, Albanian, Romanian, Bosnian, Serbian, and Croatian translation of the summary see Supplementary Materials section.

Background Malaria is one of the leading causes of acute febrile illness (AFI) in Africa. With the advent of malaria rapid diagnostic tests, misdiagnosis and co-morbidity with other diseases has been highlighted by an increasing number of studies. Although arboviral infections and malaria are both vector-borne diseases and often have an overlapping geographic distribution in sub-Saharan Africa, information about their incidence rates and concurrent infections is scarce. Methods From July 2009 to March 2013 patients from seven healthcare facilities of the Kedougou region presenting with AFI were enrolled and tested for malaria and arboviral infections, i.e., yellow fever (YFV), West Nile (WNV), dengue (DENV), chikungunya (CHIKV), Crimean Congo haemorrhagic fever (CCHFV), Zika (ZIKV), and Rift Valley fever viruses (RVFV). Malaria parasite infections were investigated using thick blood smear (TBS) and rapid diagnostics tests (RDT) while arbovirus infections were tested by IgM antibody detection (ELISA) and RT-PCR assays. Data analysis of single or concurrent malaria and arbovirus was performed using R software. Results A total of 13,845 patients, including 7387 with malaria and 41 with acute arbovirus infections (12 YFV, nine ZIKV, 16 CHIKV, three DENV, and one RVFV) were enrolled. Among the arbovirus-infected patients, 48.7 % (20/41) were co-infected with malaria parasites at the following frequencies: CHIKV 18.7 % (3/16), YFV 58.3 % (7/12), ZIKV 88.9 % (8/9), DENV 33.3 % (1/3), and RVF 100 % (1/1). Fever ≥40 °C was the only sign or symptom significantly associated with dual malaria parasite/arbovirus infection. Conclusions Concurrent malaria parasite and arbovirus infections were detected in the Kedougou region from 2009 to 2013 and need to be further documented, including among asymptomatic individuals, to assess its epidemiological and clinical impact.

Pandemic arboviruses have emerged as a major global health problem in the past four decades. Predicting where and when the next arbovirus epidemic will occur is a challenge, but history suggests that arboviral black swan events (epidemics that are difficult to predict and that have an extreme effect) will continue to occur as urban growth and globalisation expand. We briefly review unexpected arbovirus epidemics that have occurred in the past 50 years, with emphasis on the American and Pacific regions, to illustrate their unpredictability, and to highlight the need for improved global preparedness, including laboratory-based surveillance, prevention, and control programmes.

In 2005, chikungunya virus was recorded in the Indian Ocean islands, and from the end of 2013, reached the Caribbean.1 In 2014, concomitant outbreaks have happened in the Pacific due to dengue virus, chikungunya virus, and Zika virus--another mosquito-borne virus that mostly causes mild fever, joint pain, conjunctivitis, and rash.2-4 Substantial changes in epidemiology of mosquito-borne diseases in tropical oceanic regions are probably caused by many and difficult to address factors.

Key aspects of 36 mosquito-borne arboviruses indigenous to Africa are summarized, including lesser or poorly-known viruses which, like Zika, may have the potential to escape current sylvatic cycling to achieve greater geographical distribution and medical importance. Major vectors are indicated as well as reservoir hosts, where known. A series of current and future risk factors is addressed. It is apparent that Africa has been the source of most of the major mosquito-borne viruses of medical importance that currently constitute serious global public health threats, but that there are several other viruses with potential for international challenge. The conclusion reached is that increased human population growth in decades ahead coupled with increased international travel and trade is likely to sustain and increase the threat of further geographical spread of current and new arboviral disease.