How infectious agents spread to cause disease

So we now know why it is important to understand the pathology of an infectious agent. But how do they spread and cause disease?

Chain of infection

In order for an infectious agent to successfully spread from one host to another, several conditions must be met. This is referred to as the chain of infection. If this ‘chain’ is broken at any stage, the infection cannot spread and becomes contained. We will use the basic human flu as an example in the Chain of Infection activity to explain the chain of infection.

What is a Vector?

Some diseases are spread via a vector – an organism which carries the disease from one host to another. Malaria is caused by Plasmodium type protozoa but spread by mosquitoes. Mosquitoes suck contaminated blood from an infected host, and subsequently transfer the infectious agent to a new uninfected host through its bite. Mosquitoes therefore are a vector in this case. Vectors are sometimes essential in the infectious agent lifecycle.

Your Task

Now, try constructing the chain of infection for Measles. Share your ideas in the discussion area. If you are feeling creative, you can sketch a chain similar to the one we have provided, save it in Google drive, and share a link. Other image sharing guidelines are provided here.