Patient description: A 17 year old boy complains of vomiting, non-bloody diarrhea, abdominal pain, fever, chills and loss of appetite for the past 3 days. He ate a salad at a restaurant prior to his diarrhea onset. Physical exam was remarkable for pallor, jaundice, and diffuse abdominal tenderness. Lab results were as follows: Hemoglobin: 9.7 g/dL Platelet: 110,000 /cu.mm Creatinine: 3.6 mg/dL blood urea nitrogen (BUN): 73 mg/dL direct bilirubin: 2.4 mg/dL lactate dehydrogenase (LDH): 881 IU/L (normal: 110-265 IU/L) Peripheral blood smear showed a moderate number of schistocytes and helmet cells. Shiga-like toxin-producing E. coli (STEC) stx1/stx2 were found in stools. He has no other underlying disease and he is not on any medications.

Clinical trial eligibility criteria: eligible ages (years): 0.5-65.0,  Malaria, Falciparum (COHORT STUDY) 1. Age 6 months to 65 years, inclusive 2. Resident of Kenieroba with no plans to relocate away from Kenieroba for 1 year 3. Willingness to participate in the study as evidenced by informed consent (if <18 years, the informed consent of parent or guardian of the child, and assent from children 14 to 17 years old)  (COHORT STUDY) 1. Any condition that in the opinion of the investigator would render the participant unable to comply with the protocol (e.g., psychiatric disease) 2. Any health condition that in the opinion of the investigator would confound data analysis or pose unnecessary exposure risks to study personnel (e.g., individuals who are known to be HIV-infected) or to the participant (e.g., severe malnutrition) 3. Pregnancy for venous blood collections (March 2013, October 2013, March 2014) (ADULT BLOOD STUDY) 1. Age 18 to 65 years, inclusive 2. Hb level greater than or equal to 8.5 g/dL 3. Willingness to participate in the study as evidenced by informed consent (ADULT BLOOD STUDY) 1. Pregnancy 2. Any condition that in the opinion of the investigator would render the participant unable to comply with the protocol (e.g., psychiatric disease) 3. Any health condition that in the opinion of the investigator would confound data analysis or pose unnecessary exposure risks to study personnel (e.g., individuals who are known to be HIV-infected) or to the participant (e.g., severe malnutrition) (PARASITIZED BLOOD STUDY): 1. Age 2 to 17 years, inclusive 2. Hb level greater than or equal to 8.5 g/dL 3. Previous enrollment in cohort study on protocol #08-I-N120 4. Uncomplicated malaria* 5. P. falciparum density greater than or equal to 10,000/microliters 6. Known hemoglobin type HbAA or HbAS 7. Not enrolled in this protocol s cohort study 8. Willingness to participate in the study as evidenced by informed consent and assent from children 14-17 years old) Uncomplicated malaria: axillary temperature >37.5 degrees Celcius or history of fever in the past few days and no of SM (see next paragraph) and no other etiologies of febrile illness (e.g., respiratory tract infection) on clinical examination. Severe P. falciparum malaria: parasitemia of any density and any one of the following: coma (Blantyre coma score less than or equal to 2), convulsions (witnessed by investigator), severe prostration, severe anemia (hemoglobin less than or equal to 6 g/dl), respiratory distress, hypoglycemia (serum glucose less than or equal to less than or equal to 40 mg/dl), jaundice/icterus, shock (systolic blood pressure less than or equal to 70 mmHg, rapid pulse, cool extremities), cessation of eating and drinking, repetitive vomiting (PARASITIZED BLOOD STUDY): 1. Pregnancy 2. Any condition that in the opinion of the investigator would render the participant unable to comply with the protocol (e.g., psychiatric disease) 3. Any health condition that in the opinion of the investigator would confound data analysis or pose unnecessary risks to study participants (e.g., severe malnutrition, acquired or inherited immunodeficiency)