Chagas disease has an acute and a chronic phase. If untreated, infection is lifelong.
Acute Chagas disease occurs immediately after infection, may last up to a few weeks or months, and parasites may be found in the circulating blood. Infection may be mild or asymptomatic. There may be fever or swelling around the site of inoculation (where the parasite entered into the skin or mucous membrane). Rarely, acute infection may result in severe inflammation of the heart muscle or the brain and lining around the brain.
Following the acute phase, most infected people enter into a prolonged asymptomatic form of disease (called "chronic indeterminate") during which few or no parasites are found in the blood. During this time, most people are unaware of their infection. Many people may remain asymptomatic for life and never develop Chagas-related symptoms. However, an estimated 20 - 30% of infected people will develop debilitating and sometimes life-threatening medical problems over the course of their lives.
Complications of chronic Chagas disease may include:
- heart rhythm abnormalities that can cause sudden death;
- a dilated heart that doesn’t pump blood well;
- a dilated esophagus or colon, leading to difficulties with eating or passing stool.
In people who have suppressed immune systems (for example, due to AIDS or chemotherapy), Chagas disease can reactivate with parasites found in the circulating blood. This occurrence can potentially cause severe disease.