Clarifying Ebola: virulence vs contagion

Some experts are saying that the Ebola virus is "not highly contagious."   Many politicians are saying that it is "highly contagious."  Who is right?    

It helps to separate two factors that are being conflated:   virulence and contagion. 

Contagion:  The ability to spread from one individual to another through direct or indirect contact.
     The degree of contagiousness tells us how easily it is spread.   Ebola is not spread as easily as cold or flu viruses, because it cannot be picked up from airborne particles, like sneezes.    It is spread by direct contact of bodily fluids from an infected person onto the mucous membranes or broken skin of another person.    Thus, compared to other viruses, its contagiousness is low.

Virulence: The ability of an agent of infection to produce disease and the severity of that disease.   The virulence of a microorganism is a measure of its ability to overwhelm bodily defenses and to cause severe illness.
    This tells us how bad it is if you get it.   Ebola's virulence is very high -- once it has gained entrance into your body.

Think of it as a two-step process.   (1)  Being exposed to the virus as described under contagion.   (2)  Your body's attempt to resist the virus, plus the severity of the illness it causes.

It is quite correct to say that Ebola virus is not highly contagious and that it is highly virulent.   A cold is relatively high in contagion but low in virulence, the opposite of Ebola.

Ralph