This invention provides an electronic proximity apparatus and a surveillance method using such an apparatus for alerting individuals that are exposed to a contagious disease. When a person becomes symptomatic and is diagnosed as positive for a given contagious agent, individuals that have recently maintained a threshold proximity with respect to an infected individual are notified and advised to seek immediate medial care. Treatment of individuals in the very early phases of infection (pre-symptomatic) significantly reduces contagiousness of the infected population first exposed to the contagious disease, thus preventing spread of the disease throughout the general population.