Date Time Mosquito-borne disease risk following flooding and heavy rainfall The Department of Health is warning people living or traveling to regions impacted by recent flooding and heavy rainfall of the increased risk of mosquito-borne diseases. Tidal storm surges and flooding associated with heavy rains often produce extensive breeding habitat for mosquitoes. The standing water that remains after tidal and flood waters subside can create an ideal environment for mosquitoes to lay their eggs. Acting Medical Entomologist at the Department of Health, Dr Jay Nicholson, said that mosquito numbers and notified cases of Ross River virus (RRV) disease were already above average prior to the recent rainfall event.