If you had malaria once, can it return for a second time without being in a malaria area?
Yes. There are several ways in which malaria can come back without being re-infected again. The blood forms of the parasites can sometimes persist at low numbers, so that the patient no longer has any symptoms; if these blood forms begin to reproduce again, the patient will once again begin to feel sick and have malaria symptoms. This is known as ‘recrudescence’ and can occur as quickly as within the same year as the initial infection but also as long as fifty years later, depending on the type of malaria! Treating the infection thoroughly, and being tested for parasites after treatment, is one way to avoid recrudescence.
The other way in which malaria can come back is through ‘recurrence’, which is when the malaria parasite enters a dormant phase which resides in the liver. Again, the patient will feel no symptoms while the malaria is dormant, but once these liver stages change into the blood stages and reproduce, symptoms will reoccur. This form of relapse only occurs with Plasmodium vivax and P. ovale infections, and can be prevented through taking an additional form of medication, called primequine, at the same time as the normal malaria drugs when diagnosed. This extra medicine kills the liver forms of malaria and thus prevents recurrence. For more details on this, please see the comments I made, on behalf of Dr Etty Villanueva, on the post ‘Malaria Symptoms and Causes’, published on the 22nd of February, 2011.