Mucilaginous compound is a mucous substance secreted by the macrovirus, composed of amino acids, proteins, and DNA. The compound can transmit the viral infection to new hosts, and in the macrovirus' largest stage can be ejected in a stream from its stinger.

When the macrovirus infected the USS Voyager in 2373, mucilaginous compound was left throughout the ship. Neelix was struck by the compound, causing rapid fever and other symptoms. Mucilaginous compound was also found in one of the ship's bio-neural gel packs.

Evidently it is highly flammable; a single phaser shot can blow up a macrovirus, regardless of setting. (VOY: "Macrocosm")