21.   Often, exposure produces no symptoms whatsoever.

22.   Prion diseases take many years to spread, incubate and produce symptoms, though once symptoms appear the disease usually progresses swiftly and is always fatal.

23.   Several recent studies have suggested that PB and DEET can produce some symptoms Gulf troops have reported, and that they are especially dangerous when combined with other chemicals.

24.   Since most brain tumors produce symptoms, like headaches, that are commonly caused by far less devastating disorders, they are often ignored or dismissed as unimportant.

25.   Some plants have variegated foliage because they have been intentionally infected with a mosaic virus, a plant disease that produces the symptom of mottled leaves or flowers.

26.   That disease quickly produces symptoms, and people tend to seek immediate treatment.

27.   Tests that detect cancer cannot always discern whether the cancer is one that will ultimately kill or is an indolent tumor that might never produce noticeable symptoms.

28.   The earliest stages of macular degeneration produce no symptoms, though early signs of this irreversible condition can be detected through a complete eye examination.

29.   The diseases might not produce symptoms for years before becoming rapidly and painfully acute.

30.   The disorder is a variant of an adult disorder, Munchausen syndrome, a disorder in which victims fake illness or inflict harm on themselves to produce symptoms.