17th June 2024

Arboviruses & viral haemorrhagic fevers

Arboviruses

Arboviruses are simply arthropod-borne viruses. These include zika virus, chikungunya virus, and dengue virus. This section will focus on dengue, due to its prevalence and potential for life-threatening consequences.

Dengue, a flavivirus, is transmitted by the Aedes mosquito in the tropics and subtropics. The clinical manifestations of the virus are fever, arthralgia, and a distinctive maculopapular rash. The illness is usually self-limiting, though a small proportion of patients may develop severe, life-threatening dengue. Interestingly, past infection with one of the four serotypes of dengue increases the risk of subsequent severe dengue, likely by a process called Antibody Dependent Enhancement. This makes vaccine development difficult. The term “dengue haemorrhagic fever” was previously used to denote severe dengue, however this has been superseded by the most recent WHO classifications of dengue, with or without warning signs, and severe dengue. Serology can be used for formal diagnosis, though diagnosis in endemic regions can normally be made on clinical and laboratory findings. Leukopenia and thrombocytopenia are common. Treatment of dengue is purely supportive.

Image Source: WHO/IRIS (2009). 10665, Licensed under a creative commons licence. Available for free at: https://apps.who.int/iris/handle/10665/44188 (Accessed: 24 January 2024).

Viral haemorrhagic fevers

It is worth having a general appreciation of other viral haemorrhagic fevers. If a viral haemorrhagic fever is suspected in a returned traveller, an algorithm should be followed (see references). This considers the history of the febrile illness, the area travelled to, and any ill contacts or contacts with potential reservoirs of infection. A thorough history is necessary, as evidenced by Barr et al. (2013), where the source of infection was identified using wedding photographs.

The antiviral ribavirin may be of benefit in some viral haemorrhagic fevers, however the mainstay of treatment for viral haemorrhagic fevers is generally supportive care. It is important to note that Lassa, Ebola, and Marburg, and Crimean-Congo haemorrhagic fevers are all capable of person to person spread. Rift Valley haemorrhagic fever is generally spread via virulent livestock. Yellow fever (which is vaccine-preventable) and dengue are both arboviruses.

References

• Shastri PS, Taneja S. Dengue and Other Viral Hemorrhagic Fevers. Indian J Crit Care Med. 2021 (Suppl 2):S130-S133. doi: 10.5005/jp-journals-10071-23814
• Solomon T. Dengue and yellow fever. In: Beeching N, Gill G, ed. by. Tropical Medicine Lecture Notes. 7th ed. West Sussex: Wiley Blackwell; 2014. p. 283-288
• UK health security agency. UK viral haemorrhagic fever algorithm – https://www.gov.uk/government/publications/viral-haemorrhagic-fever-algorithm-and-guidance-on-management-of-patients (accessed April 2022)
• Barr D, Aitken C, Bell D et al. First confirmed case of Crimean-Congo haemorrhagic fever in the UK. The Lancet. 2019;382(9902), p.1458