[1][2] Depending on the type locality of the original P. ovale defined by Stephens, one of the proposed species (likely P. ovalecurtisi) may end up as a junior synonym of the old name.

[7][8] However P. ovale has also been reported in the Philippines, eastern Indonesia, and Papua New Guinea,[9] as well as in Bangladesh,[10] Cambodia,[11] India,[12] Myanmar,[13] Thailand[14] and Vietnam.

[1] While similar to P. vivax, P. ovale is able to infect individuals who are negative for the Duffy blood group, which is the case for many residents of sub-Saharan Africa.

[7] The microscopic appearance of P. ovale is very similar to that of P. vivax and if there are only a small number of parasites seen, it may be impossible to distinguish the two species on morphological grounds alone.

Among the species infecting the great apes, Plasmodium schwetzi morphologically appears to be the closest relation to P. ovale.

A second analysis suggests that these species separated 4.5 million years ago (95% confidence interval 0.5 – 7.7 Mya).

[20] A third worked sequenced the whole genome of both species, confirmed the differences and dated the split at around million years.

[22] P. ovale is introduced into the human host by the bite of an infected mosquito, in a motile form called a sporozoite.

When the mosquito feeds again, the sporozoites enter through the salivary duct and are injected into a new host, starting the life cycle again.

[7] There are situations where some of the sporozoites hypothetically do not immediately start to grow and divide after entering the hepatocyte, but remain in a dormant, hypnozoite stage[24] for weeks or months.

[25] The duration of latency is variable from one (assumed in the case of P. ovale) hypnozoite to another and the factors that will eventually trigger growth are not known; this could explain how a single infection can be responsible for a series of waves of parasitaemia or "relapses".

[26] While humans appear to be the natural mammalian host of P. ovale, chimpanzees and Saimiri monkeys have also been experimentally infected.