Insect virus transmission: different routes to persistence

•Deep sequencing has allowed for the identification of a large number of covert virus infections in insects.•The molecular basis of behavioural changes that facilitate horizontal transmission of some baculoviruses have been identified.•We have better theoretical understanding of the evolution of covert infection strategies.•Molecular mechanisms leading to persistent infections are coming to light.

Transmission is a fundamental process in disease ecology; however, the factors that modulate transmission and the dynamical and evolutionary consequences of these factors in host populations are difficult to study in natural settings. Much of our current knowledge comes from a limited number of virus groups and few ecological studies. Alternatively, progress has been made in the detection of new viruses and in probing the molecular basis of behavioural manipulation of hosts that might influence virus transmission. An expanding theoretical framework provides guidelines on the conditions under which particular transmission strategies might evolve, and their dynamical consequences, but empirical tests are lacking.