HETEROGENEITIES IN THE TRANSMISSION OF INFECTIOUS AGENTS - IMPLICATIONS FOR THE DESIGN OF CONTROL PROGRAMS

From an analysis of the distributions of measures of transmission rate s among hosts, we identify an empirical relationship suggesting that, typically, 20% of the host population contributes at least 80% of the net transmission potential, as measured by the basic reproduction numb er, R(0). This is an example of a statistical pattern known as the 20/ 80 rule. The rule applies to a variety of disease systems, including v ector-borne parasites and sexually transmitted pathogens. The rule imp lies that control programs targeted at the ''core'' 20% group are pote ntially highly effective and, conversely, that programs that fail to r each all of this group wilt be much less effective than expected in re ducing levels of infection in the population as a whole.