I am asking this in the context of web based disease monitoring system like Google Flu trends, in this case would it be right to categorize these as examples of descriptive epidemiology as they answer who, where and when questions?
Monitoring in essence is observation and description of a phenomenon or an event while time passes. If the researcher sticks to just description , it is then descriptive epidemiology. But in real life, a lot can be done on available data. Prediction of future changes can be based on current time trend studies.