A lot has changed in the 21 years since the launch of the National Collection of Pathogenic Viruses. Back in early 1999, human coronaviruses were associated with nothing more serious than the common cold, Zika virus had only been linked with around a dozen cases of human disease in 50 years, while chikungunya and West Nile viruses were considered to be relatively insignificant human pathogens.
The question of which virus will be next to make the jump from relative obscurity to frontpage news is important to ask, but difficult to answer. While there is potential for such a paradigm shift for many viruses, one group has shown a propensity to cause large outbreaks after decades of apparent inactivity or low-level circulation – the arthropod-borne viruses (arboviruses).
The NCPV catalogue contains numerous under-researched emerging and re-emerging arboviruses with the potential to cause a significant burden of human diseases should events occur that increase human-reservoir/vector interaction or alter climatic conditions. Some of the less well-known examples that could make the jump to notoriety include:
Mayaro virus (MAYV)1: A mosquito-borne alphavirus similar to chikungunya virus but with a propensity for more severe clinical symptoms including haemorrhagic manifestations. MAYV has close association with tropical forest regions of Latin America with reports of human cases increasing in recent years, possibly due to increased human activity in rainforests. MAYV is typically transmitted to humans through the bite of infected Haemagogus mosquitoes (common in rainforests), but studies indicate Aedes aegypti and Aedes albopictus are also likely competent vectors raising the potential for the virus to become established in many countries across Asia, Africa, Europe and North America.
Ngari virus (NGIV)2: A mosquito-borne bunyavirus endemic to many areas of Africa capable of causing a febrile illness with severe haemorrhagic manifestations in humans. The virus has been isolated from a wide range of mosquitoes including several species of Aedes, Anopheles and Culex mosquitoes. Although human cases are rare, outbreaks of haemorrhagic fever resulting from NGIV have been reported in Kenya, Somalia and Mauritania. Curiously, NGIV is a natural reassortant virus with two genome segments from Bunyamwera virus (S + L segments) and one from Batai virus (M segment); curiously, NGIV can result in a severe haemorrhagic disease despite neither donor virus being associated with significant clinical illness. Given the severity of disease resulting from this virus, and the wide range of mosquito species that can transmit the virus to human, it is fortunate that so few cases have been reported.
O’nyong-nyong virus (ONNV)3: A mosquito-borne alphavirus endemic to central regions of Africa. ONNV is one of the few arboviruses transmitted by anopheline mosquitoes which typically feed at night time. Clinical symptoms include rash, severe arthralgia, and possibly mild haemorrhagic manifestations – the joint pain associated with human infection can last many months and is frequently extremely painful. Reports of human cases are rare although this could be due to misdiagnosis as symptoms are similar to the more ‘well-known’ chikungunya virus, and few affected individuals have diagnostic confirmation to support initial diagnosis. While few cases have been reported in recent years, ONNV has significant outbreak potential with several large epidemics reported including at least 2 million cases estimated from an outbreak in 1959-1962.
Oropouche virus (OROV)4: A midge-borne bunyavirus endemic to many regions of South America that typically results in a mild, self-limiting illness, but can also cause severe disease with neurological and haemorrhagic manifestations. More than 500,000 cases have been reported in the last 60 years, but there is significant potential for misdiagnosis due to the clinical similarity with other circulating pathogens including dengue, yellow fever and malaria; therefore, the true meaning the true burden of disease is likely underestimated. OROV is typically transmitted by midges, in particular Culicoides paraensis, although mosquitoes such as Culex quinquefasciatus, Coquillettidia venezuelensis and Aedes serratus may be competent secondary vectors. If OROV adapts for more efficient transmission by these mosquito species, the virus could become a public health concern in many more countries.
Usutu virus (USUV)5: A mosquito-borne flavivirus closely related to West Nile virus (WNV) endemic to large regions of Africa with reports of detection in European countries increasing in recent years. Like WNV, USUV can infect many wild, captive and migratory birds leading to significant die-off events; the fact that USUV can infect migratory birds means the potential for introduction into new regions is significant. USUV is generally considered mild or asymptomatic in humans, but reports of encephalitis are emerging as more detailed investigations are performed. Ominously, our current view of USUV is similar to the understanding of WNV in the early 1990s before establishment of WNV firstly in Europe and then in North and South America.
NCPV is keen to support research into rare emerging and remerging viruses, including arboviruses, and offers a wide variety of authenticated viral isolates to the research community. We are also looking to expand our range of rare pathogenic viruses and would welcome potential accessions – please contact us at: email@example.com if you can help.
1. Pereira, T. N., Carvalho, F. D., De Mendonça, S. F., Rocha, M. N. & Moreira, L. A. Vector competence of Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus mosquitoes for Mayaro virus. PLoS Negl. Trop. Dis. 14, (2020).
2. Dutuze, M. F., Nzayirambaho, M., Mores, C. N. & Christofferson, R. C. A Review of Bunyamwera, Batai, and Ngari Viruses: Understudied Orthobunyaviruses With Potential One Health Implications. Front. Vet. Sci. 5, (2018).
3. Rezza, G., Chen, R. & Weaver, S. C. O’nyong-nyong fever: a neglected mosquito-borne viral disease. Pathog. Glob. Health 111, 271–275 (2017).
4. Sakkas, H., Bozidis, P., Franks, A. & Papadopoulou, C. Oropouche Fever: A Review. Viruses 10, (2018).
5. Clé, M. et al. Usutu virus: A new threat? Epidemiol. Infect. 147, (2019).
Written by Dr Barry Atkinson
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