Figure 2. Electricity-free typhoid diagnostic approach.

a. packets containing a phase-change material are heated in water or direct sunlight. b. after heating the phase change packet (right), the material appears as a clear liquid (left). c. phase change packets and bottles, containing blood from typhoid suspects and vancomycin additive, are placed into a insulated container. d. bottles are inspected every 24 hours for color change of a CO₂ detector, which distinguishes positive (left) from negative (right) cultures.