Before revision:  Our results call for the need for contact tracing to go both backward and forward, in multiple steps, to leverage all forms of positive biases .  Using simulations on networks with a power-law degree distribution , we show that this deep contact tracing can potentially prevent almost all further transmissions even at a small probability of detecting infected individuals  .
After revision:  Our results call for the need for contact tracing to go both backward and forward, in multiple steps, to leverage all forms of positive biases . The effectiveness of backward tracing is due to simple but overlooked biases arising from the heterogeneity in contacts. Using simulations on networks with a power-law degree distribution , we show that this deep contact tracing can potentially prevent almost all further transmissions even at a small probability of detecting infected individuals .