Spanish bee researchers (Higes et al.) reported that the new pathogen was discovered in 2005 in Spain and was observed to have a notably higher virulence than the western version.

Ideal characteristics of a biological agent to be used as a weapon against humans are high infectivity, high virulence, non-availability of vaccines, and availability of an effective and efficient delivery system.

Through viremia, some nephrotropic strains (most of high virulence) could infect the kidney epithelium in tubules and nephron, causing kidney failure.

"People are trying to understand which of those mutations was responsible for human-to-human transmission and high virulence in humans," Dr. Holmes said of one of the fundamental unanswered questions about SARS.

Due to its ease of spread by aerosol and its high virulence.

Other studies say Soviet military labs also tested typhus, botulinum toxin, Venezuelan equine encephalitis, smallpox, and microbial strains with characteristics useful in warfare, like high virulence and resistance to ultraviolet rays or heat.

However, the host, being the parasite's resource and habitat in a way, suffers from this higher virulence.

Any movement on the virulence axis, towards higher or lower virulence, will result in lower fitness for the parasite, and thus will be selected against.

The adjoining of these two pathways could allow a consistently high virulence of S. pyogenes despite a variety of environmental conditions.

In fish, the incubation period of L. garvieae is very brief and the microorganism performs with high virulence.