1. A computer implemented method of measuring a plurality of individual entities' infectivity, susceptibility and baseline infection risk (or baseline adoption likelihood) to biological or social contagions, which may involve single or multiple diseases, products or behaviors, and those entities' sensitivity to environmental factors, comprising: obtaining the contact relation matrix data of a plurality of potentially interacted individual entities wherein the matrix element represents the physical contact in disease contagion or any form of communication in social contagion between any two individual entities; obtaining the sequence of infection or adoption occurrences data for single or multiple diseases, products or behaviors of each individual entity during the observation period; pairing the infection or adoption occurrences of single or multiple diseases, products or behaviors of any two individual entities, wherein one is the prior infection or adoption status of another one's infection or adoption status at an occasion during the observation period; obtaining data of the conditions of environmental and other observable factors confronted by any of two individual entities during the observation period, and inferring each individual entity's infectivity and susceptibility to contagion, their baseline infection risk (or adoption likelihood) to single or multiple diseases, products or behaviors, and sensitivity to environmental factors, based at least in part on maximizing the conditional infection probability of each susceptible individual entity that is determined by a baseline infection risk (or Baseline adoption likelihood) plus a product of (i) potential infectious entity's infectivity and infection status, (ii) potential susceptible entity's susceptibility, (iii) contact relation between any two potentially interacted entities, and (iv) environmental conditions.