If viruses invade cells but do not produce overt signs of an infection, the infection is in the stage.

If viruses invade cells but do not produce overt signs of an infection, the infection is in the latent stage. In addition, the latent or latency period may be one and the same in which a difference is completed among incubation period in which it is the period among infection and onset of the disease and latent period is the time from infection to infectiousness. 

Long term continuous groundwater monitoring, especially with warning systems and anthropic activity monitors