Complex sentence: Misdiagnosis is frequently a concern especially in cases with abdominal pain, in countries where Lassa is common, Lassa fever is often misdiagnosed for example as appendicitis and intussusception which delays treatment with the antiviral ribavirin.
Split into simpler sentences: Misdiagnosis is frequently a concern especially in cases with abdominal pain. In countries where Lassa is common, Lassa fever is often misdiagnosed as appendicitis and intussusception which delays treatment with the antiviral ribavirin.