This episode explores two important families of enveloped positive-sense RNA viruses frequently transmitted by arthropod vectors. Drawing from Murray’s Chapter 52, it examines how ecological cycles shape viral epidemiology.

The togaviruses include rubella virus and various alphaviruses. Rubella produces mild disease in children but poses serious risk during pregnancy, leading to congenital rubella syndrome. Alphaviruses often cause febrile illness with arthralgia.

The flaviviruses include:

* Dengue virus

* Zika virus

* Yellow fever virus

* West Nile virus

* Japanese encephalitis virus

Transmission typically involves mosquitoes or ticks. Pathogenesis often includes viremia, endothelial involvement, and immune-mediated injury. Some flaviviruses are neurotropic; others are hepatotropic or haemorrhagic.

Conceptually, these viruses illustrate how vector ecology determines geographic distribution and outbreak patterns. Clinically, supportive care is often primary, though vaccination exists for selected members.

Key Takeaways

* Togaviruses and flaviviruses are enveloped positive-sense RNA viruses

* Many are transmitted by mosquitoes or ticks

* Rubella can cause congenital infection

* Flaviviruses may cause haemorrhagic or neurologic disease

* Vector control is central to prevention

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