The Quazulu VIII virus was a respiratory ailment that produced cold-like symptoms. The ailment was transmitted by an airborne particle whose sweet scent, which was similar to the Klingon plant Night blooming throgni, inspired deep inhalation. Once inside the host's body, the particle became the virus. The virus mutated every twenty minutes.
In 2364, this virus became known to Starfleet when twelve students from the USS Enterprise-D went on a field trip to Quazulu VIII, where they were exposed to this virus. Later, it was spread among the crew of the Enterprise on their way to and in orbit of Angel I. Doctor Beverly Crusher developed an inoculant to the virus and cured the crew. (TNG: "Angel One")