Stevens has found that microglia play a role in synapse loss in a range of disease states, including West Nile virus infection[12] and neurodegenerative diseases such as Alzheimer's disease,[13] where synapse loss precedes neuron death.[14] Microglia may contribute to disease both by phagocytosing synaptic material [13] and activating neurotoxic astrocytes.[15] Her research indicates that neurodegenerative diseases may represent a local reactivation of microglial pruning pathways that are beneficial during development but detrimental in the mature brain.