In this lesson, you will learn about German measles, rubella, and three closely related viruses called Eastern equine encephalitis, Western equine encephalitis, and Venezuelan equine encephalitis, as well as their serious consequences.
The Togaviridae Virus Family
While some viruses may be named after a certain animal, that doesn’t necessarily mean humans will get away scot-free if they are affected by that animal-sounding disease. That’s because some diseases are zoonotic, or capable of being transmitted from an animal to a human. In fact, there is more than one such disease-causing virus in this family that can kill a human. Let’s see what I mean as we explore Togaviridae structure, transmission, and disease.
Togaviridae Structure and Transmission
The viruses in this family have a single-stranded, positive-sense RNA genome enclosed in an icosahedral capsid that is itself enclosed in an envelope.They can be transmitted in one of numerous ways. The first virus we are going to talk about is transmitted through a horizontal route of transmission, namely the respiratory route.
Basically, if an infected person coughs or sneezes, then you may get infected yourself.Other viruses in this family can be spread through arthropod vectors. Arthropod vectors are things like mosquitoes, ticks, and so on. Therefore, certain togaviruses are known as arboviruses since arboviruses are spread by arthropods.
Rubella and German Measles
One of the more well-known diseases in this family is known as rubella. This is a mild disease caused by the rubella virus that is characterized by a fever and rash typically in children and young adults. Another name for rubella is German measles.
Now, I know that sounded pretty straightforward – I mean, it’s just a rash, for crying out loud, that will go away fairly quickly. Big deal. That’s right; it is a big deal. That’s because another way of transmitting the rubella virus is vertically.
Vertical transmission in the case of rubella occurs when a pregnant mother, who never had rubella nor was vaccinated for it, gets infected with the rubella virus and passes it on to her unborn child. The most critical time of infection is during the first three months of pregnancy.If this type of vertical transmission occurs, the child can be born with something known as congenital rubella syndrome, or CRS for short. Babies born with this condition can be born deaf and unable to see and may have all sorts of intellectual disabilities and even seizures.
The Arboviral Encephalitides
Speaking of seizures, I did mention before that some viruses in this family are arboviruses. The main arthropod involved in the arboviruses of this family is the mosquito, and some of these mosquitoes can carry viruses that can lead to inflammation of the brain, known as encephalitis, which will lead to seizures in some cases.The three closely related encephalitis-causing viruses of the Togaviridae family are known as the Eastern, Western, and Venezuelan equine encephalitis viruses.
I know you just had a brain freeze. We’re talking about humans, yet these diseases are implying equine, or horse, disease.Well, that’s because these viruses were first identified in horses, but they can also infect a human if an infected mosquito were to bite one.The problem is that infection by these viruses, especially the Eastern equine encephalitis virus, can cause death.
One-third of all people who suffer from clinical encephalitis caused by the Eastern equine encephalitis virus will die, and the survivors may have permanent brain damage that will leave them virtually incapacitated. In fact, it’s so deadly that this virus was once considered as a potential biological weapon by more than one nation.
Thankfully, you don’t have to fear a dirty bomb of that sort since those weapons programs were suspended, or so I hope, and we can instead focus our attention on reviewing the important concepts of this lesson.One of the more well-known diseases in this family is known as rubella.
This is a mild disease caused by the rubella virus that is characterized by a fever and rash typically in children and young adults. Another name for rubella is German measles.A congenital form of rubella can cause seizures just like the three closely related encephalitis-causing viruses of the Togaviridae family, known as the Eastern, Western, and Venezuelan equine encephalitis viruses.
Upon completing this lesson, you will be able to:
- Describe the structure of the viruses in the Togaviridae family and how they are transmitted
- Explain the differences in rubella and its congenital form
- Summarize the potential effects of the encephalitis-causing Togaviridae viruses