Of the huge number of individuals infected by E. histolytica, about 10% become symptomatic and develop colitis and liver abscesses, resulting in a mortality rate estimated between 40,000 and 120,000 persons a year.
Patients infected with pathogenic E. histolytica may show a wide range of conditions. Some may be asymptomatic; others may show mild diarrhea that develops into bloody diarrhea and eventually fulminant colitis.