Predicting the SARS-CoV-2 effective reproduction number using bulk contact data from mobile phones

Area of Science:

• Epidemiology
• Public Health
• Network Science

Background:

• Nonpharmaceutical interventions, including social distancing, have been crucial in controlling SARS-CoV-2 surges.
• Understanding individual contact behavior is essential for predicting and managing infectious disease transmission.
• Traditional metrics may not fully capture the complexity of social interactions influencing disease spread.

Purpose of the Study:

• To analyze individual contact behavior using anonymized GPS data in Germany.
• To develop and validate a metric, the contact index (CX), for assessing contact patterns.
• To evaluate the predictive power of CX for the effective reproduction number (R) of SARS-CoV-2.

Main Methods:

• Analysis of deidentified Global Positioning System (GPS) tracking data from 1.15 to 1.4 million German cell phones daily (March-November 2020).
• Application of graph sampling theory to estimate the contact index (CX), quantifying contact number and heterogeneity.
• Statistical evaluation of the correlation between CX and the effective reproduction number (R) derived from case numbers.

Main Results:

• The contact index (CX), reflecting contact heterogeneity, proved to be a more accurate predictor of the effective reproduction number (R) than total contact counts.
• A strong correlation was observed between CX and R, with a lag of over two weeks, allowing early detection of behavioral impacts on transmission.
• The study identified a critical CX threshold indicating a potential rise in R above 1, signifying increased transmission risk.

Conclusions:

• Contact heterogeneity, as measured by CX, is a key factor in SARS-CoV-2 transmission dynamics and superspreading events.
• CX provides an early warning system for changes in transmission rates, enabling proactive public health interventions.
• The findings support the use of CX to optimize and leverage social distancing measures for future pandemic control.