What these inoculated parasites, called "sporozoites", do in the skin and lymphatics, exactly, has yet to be accurately determined. However, a percentage of sporozoites follow the bloodstream to the liver, where they invade hepatocytes. They grow and divide in the liver for 2–10 days, with each infected hepatocyte eventually harboring up to 40,000 parasites. The infected hepatocytes break down, releasing this invasive form of Plasmodium cells, called "merozoites" into the bloodstream. In the blood, the merozoites rapidly invade individual red blood cells, replicating over 24–72 hours to form 16–32 new merozoites. The infected red blood cell lyses, and the new merozoites infect new red blood cells, resulting in a cycle that continuously amplifies the number of parasites in an infected person. However, most of the P. vivax replicating merozoite biomass is now (since 2021) known to be hidden in the spleen and bone marrow (perhaps elsewhere too), thereby supporting the astute, long-standing (since 2011) but previously ignored theory that non-circulating merozoites are the source many P. vivax malarial recurrences (see “Recurrent malaria” section below). Over rounds of this red blood cell infection cycle in the bloodstream and elsewhere, a small portion of parasites do not replicate, but instead develop into early sexual stage parasites called male and female "gametocytes". These gametocytes develop in the bone marrow for 11 days, then return to the blood circulation to await uptake by the bite of another mosquito.
ITNs and IRS may not be sufficient to eliminate the disease, as these interventions depend on how many people use nets, how many gaps in insecticide there are (low coverage areas), if people are not protected when outside of the home, and an increase in mosquitoes that are resistant to insecticides. Modifications to peoples houses to prevent mosquito exposure may be an important long term prevention measure. Insecticide-treated nets
Mosquito nets help keep mosquitoes away from people and reduce infection rates and transmission of malaria. Nets are not a perfect barrier and are often treated with an insecticide designed to kill the mosquito before it has time to find a way past the net. Insecticide-treated nets (ITNs) are estimated to be twice as effective as untreated nets and offer greater than 70% protection compared with no net. Between 2000 and 2008, the use of ITNs saved the lives of an estimated 250,000 infants in Sub-Saharan Africa. About 13% of households in Sub-Saharan countries owned ITNs in 2007 and 31% of African households were estimated to own at least one ITN in 2008. In 2000, 1.7 million (1.8%) African children living in areas of the world where malaria is common were protected by an ITN. That number increased to 20.3 million (18.5%) African children using ITNs in 2007, leaving 89.6 million children unprotected and to 68% African children using mosquito nets in 2015. Most nets are impregnated with pyrethroids, a class of insecticides with low toxicity. They are most effective when used from dusk to dawn.