The Australian cockroach is an omnivore that scavenges for food. It is a common pest in homes and can transmit disease by contaminating food. A number of pathogenic organisms have been associated with cockroaches. Ingested bacteria can survive in the cockroach's digestive system, sometimes for months or even years, and are passed in its droppings. Cockroaches will vomit and defecate on food and it is thought that disease may be transmitted to humans when humans eat food contaminated by this species. If the population becomes dense, it can produce a distinct odor. Food and utensils can be contaminated with droppings, cast skins, empty egg cases, and vomit marks.