Virulent (from lat. virus poison; lat. lateo hide; hide) - a living virulent microorganism or its fragment that can cause disease in warm-blooded animals (especially susceptible ones) and are the cause of infectious diseases.
The virulence of a microorganism can be defined as “the degree to which a given specific strain produces a characteristic or pathogenic response.” Accordingly, determination of virulence requires some kind of biological test and, possibly, specification of the host species. Thus, the virulent effect of microbes is one of the causes of the disease mechanism. The cause of the disease always lies in the presence in the body of a living source of infection - a microbe - or a virus. It can be in the form of an infectious or non-infectious form, capable of functioning or losing its pathogenic properties under the influence of a number of factors. The degree of destruction is reflected in the term "virulence". Consequently, it is a kind of indicator of the viability of a microorganism. In other words, virulence represents all the qualities of an organism that enable it to reproduce and spread throughout the human population. One unit dose of a pathogen requires a strictly defined number of susceptible individuals.