The pathways of epidemics

A new computer model rapidly and accurately estimates who spreads an infection particularly extensively, thereby facilitating countermeasures

Epidemics could be more effectively contained in the future. A new computer-aided method developed by researchers of the Max Planck Institute for Mathematics in the Sciences in Leipzig identifies those persons in the population who propagate an infection most strongly. In contrast to other methods, this process is distinguished by significantly less computational effort than comparably precise ones in estimating the actual number of people who are directly or indirectly infected by a specific person.

Other fast calculation methods provide solely a qualitative ranking of carriers, but do not enable statements to be made concerning how many more people a contagious person infects in comparison to a less virulent carrier. This information is especially important if a vaccine is in short supply. In that event, physicians need to know which persons they should preferentially vaccinate to most effectively prevent a pandemic.

It is difficult to predict who transmits an infection most actively. Contagious persons who have contact with many other people do not always infect the most number of people. The efficiency with which an individual propagates pathogens of a disease depends upon how directly interconnected the person is, and while this is largely correct, it applies only under certain conditions.

''There are people as well who are less directly interconnected and yet propagate an infection quite extensively,'' says Joseph Lizier, from the Max Planck Institute for Mathematics in the Sciences, who investigated the spread of epidemics and is now a post-doctoral Fellow at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Sydney.

Since it is not easy to identify which properties of social networks are pivotal for the spread of an infection, Lizier, a computer scientist, and mathematician Frank Bauer investigated these characteristics more closely. The population of a region, a country, or even the world can be regarded as examples of a social network.