We usually use the term virulence. But how one can measure it?
wikipedia has enough information on the topic. check the following link
It is the degree of pathogenicity of an organism and is also a relative term. That is the relative ability of a pathogen to cause disease. While discussing disease, the adjective virulent is used to describe effect severity, and in discussing pathogens, the degree of infectiousness.
Arg.. Thanks for giving the link but I want to know how to measure it? Its not given at the link advices by you.
Do you mean quantitation of virulence??????????
I did some google searching and found a book page describing the quantitation of the virulence
I hope this will answer your question more clearly
Testing for virulence varies depending on the pathogen you are looking to test. Regardless of how it is done, the most important consideration when talking about virulence is that you need to test for the ability of the pathogen to cause disease, which means that unfortunately molecular methods like real time PCR, which quantify the amount of nucleic acids present, cannot provide a direct measure of virulence (because the RNA/DNA of a dead pathogen would still show up, even though it cannot cause disease).
The traditional way of testing for virulence is to infect a given organism (rabbits, pigs, chickens, etc), typically one that has been previously shown to be a good model for the way the disease progresses in humans, and determine if the amount of pathogen injected was enough for it to colonize and spread (and consequently cause disease). Another way to do the same is to inoculate that same pathogen into a cell culture system. Virulence is basically derived from a relationship between how little pathogen is necessary to cause infection and disease. The way this is measured varies, but one typical way is to simply visualize the cultured cells to determine how many have been infected, or obtain a bleed from the animal and titer how much pathogen is present (and then compared it to how much was inoculated).
To follow up on Ivan's post, try searching the key term "ID50", which is the dose of a pathogen sufficient to produce a sustained infection in 50% of a population of animals tested. This is the usual quantitative index of infectivity, a component of virulence.
Also, you can perform in vivo studies with your pathogen of interest and compare it to uninfected, non-pathogenic and high pathogenic viruses to see how it compares.