Network Science

COVID-19 Infection Risk Estimation Based on Contact Data

We present CRISP (COVID-19 Risk Score Prediction), a probabilistic graphical model for COVID-19 infection spread through a population based on the SEIR model where we assume access to (1) mutual contacts between pairs of individuals across time across various channels (e.g., Bluetooth contact traces), as well as (2) test outcomes at given times for infection, exposure and immunity tests. Our micro-level model keeps track of the infection state for each individual at every point in time, ranging from susceptible, exposed, infectious to recovered. We develop a Monte Carlo EM algorithm to infer contact-channel specific infection transmission probabilities. Our algorithm uses Gibbs sampling to draw samples of the latent infection status of each individual over the entire time period of analysis, given the latent infection status of all contacts and test outcome data. Experimental results with simulated data demonstrate our CRISP model can be parametrized by the reproduction factor R0 and exhibits population-level infectiousness and recovery time series similar to those of the classical SEIR model. However, due to the individual contact data, this model allows fine grained control and inference for a wide range of COVID-19 mitigation and suppression policy measures. Moreover, the algorithm is able to support efficient testing in a test-trace-isolate approach to contain COVID-19 infection spread.


Herbrich, Ralf; Rastogi, Rajeev; Vollgraf, Roland

CRISP: A Probabilistic Model for Individual-Level COVID-19 Infection Risk Estimation Based on Contact Data Journal Article

In: arXiv:2006.04942, 2020.

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Predicting Information Spreading in Twitter

We present a methodology for predicting the spread of information in a social network. We focus on the Twitter network, where information is in the form of 140 character messages called tweets, and information is spread by users forwarding tweets, a practice known as retweeting. Using data of who and what was retweeted, we train a probabilistic collaborative filter model to predict future retweets. We find that the most important features for prediction are the identity of the source of the tweet and retweeter. Our methodology is quite flexible and be used as a basis for other prediction models in social networks.


Zaman, Tauhid R; Herbrich, Ralf; Gael, Jurgen Van; Stern, David

Predicting Information Spreading in Twitter Proceedings Article

In: Proceedings of Computational Social Science and the Wisdom of Crowds Workshop, 2010.

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De-Layering Social Networks

Traditionally, social network analyses are applied to data from a particular social domain. With the advent of online social networks such as Facebook, we observe an aggregate of various social domains resulting in a layered mix of professional contacts, family ties, and different circles. These aggregates dilute the community structure. We provide a method for de-layering social networks according to shared interests. Instead of relying on changes in the edge density, our shared taste model uses content of users to disambiguate the underlying shared interest of each friendship. We successfully de-layer real world networks from LibraryThing and, obtaining topics that significantly outperform LDA on unsupervised prediction of group membership.


Dietz, Laura; Gamari, Ben; Guiver, John; Snelson, Edward; Herbrich, Ralf

De-Layering Social Networks by Shared Tastes of Friendships Proceedings Article

In: International AAAI Conference on Web and Social Media, 2012.

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