In addition, the various versions of PPI-1v were shown to impact on virulence differently and suggests that this region is at least partly responsible for the greater virulence of highly virulent isolates compared to less virulent isolates.
However, it is possible that other factors possessed by the hyper-virulent lineage I/II group strains are responsible for their greater virulence in humans, and remain to be discovered.
"The very efficiency that is involved here means that if a crisis were to occur, that that crisis is transmitted at a far faster pace and with some greater virulence," he said.
They worry that the disease is really still present, slowly being transmitted among people who do not become very sick, and will burst loose again next autumn and winter, perhaps with even greater virulence.
According to what is known about the phylogenetic relationships of Plasmodium species, P. falciparum is the most recent of the human parasites, which may help to explain its greater virulence.
Quammen's sprawling scientific adventure tracks these diseases from the jungles of Central Africa to the rooftops of Bangladesh and the caves of southern China, and warns that such crossovers are bound to occur with more frequency, and possibly greater virulence.
What they have in common is that they are all zoonoses — animal infections that jump over into humans — and the book's unsettling thesis is that such crossovers are bound to happen with more frequency, and possibly greater virulence, as people increasingly encroach on formerly wild and undisturbed habitats.
The greater virulence of P. falciparum is associated with its tendency to infect a large proportion of the red blood cells; patients infected with that species will exhibit ten times the number of parasites per cubic millimetre of blood than patients infected with the other three malaria species.
Transparent (T) variants are more efficient in colonizing the nasopharynx while opaque (O) variants exhibit greater virulence during systemic infections.
Transparent (T) phase variants are more efficient in colonizing the nasopharynx while the opaque (O) phase variants exhibit greater virulence during systemic infections.
