What is the incubation period of n fowleri? why do some sites say 1-7 and others go up to 15 days? seems most cases are 7 or less when symp show

Too rare to worry: Naegleria fowleri encephalitis is so rare that only a few cases have been studied, so it is understandable that estimates of incubation period may vary widely. But it really shouldn't matter. You cannot have it if you haven't been swimming in freshwater ponds or lakes. Even if you have done that, there are only an average of 1-2 cases per year in the entire US. You aren't likely to be one of them!

N. fowleri: CDC states Sx's start 1-9 days (median 5 days) AFTER EXPOSURE. People usually die 1-18 days (median 5 days) AFTER START of SYMPTOMS. These are two different statstics. Because there have only been 143 cases in the US between 1962 & 2017 - new cases may make slight changes in overall stats. There have even been some recent survivors! REF: https://www.cdc.gov/parasites/naegleria/illness.html