Figure 1.
The image displays a dense collection of identical black human-like figures arranged in a grid pattern. Among these figures, there is one distinct red figure located near the right of the grid. The red figure stands out due to its different color, indicating a unique or different status compared to the black figures. The image likely represents a concept where the majority are unaffected, while a small minority experiences a significant difference.
Infection enigma. All the individuals shown have been infected with the same microbe. Only one displayed life-threatening disease (red). The others had silent infections or developed benign, self-healing illness (black). This is a representation of the infection enigma, a problem posed around 1900. This problem applies to all of the ~3,000 known human infections. The proportion of life-threatening cases is typically small, as only a dozen infections are currently known to trigger severe disease in >10% of infected individuals (2, 3, 6).