The Unthor Pandemic was an epidemiological and terrorist crisis from December 3273 to early November 3274 on the planet Unthor that caused widespread mortality and economic disruption, and is among the worst single instances of a mass disease crisis of the 33rd century. The crisis arose from the emergence of a viral haemorrhagic fever in the planet's frontier human settlement centers in late 3273. The disease spread rapidly due to mass transit between frontier settlements and the main cities, before symptoms even became apparent. After its detection in January 3274, mass transit was shut down and quarantines were placed. By the middle of 3274, the planet had seen severe population reductions and colonist enrollment had ceased, threatening the long-term viability of the colony. Special teams of doctors, scientists, and field researchers were dispatched to investigate the causes of the disease and develop a vaccine. The superficial similarity of the disease to Ebola, its affecting solely the human colonist population, and the geopolitical situation of planet Unthor were all clues that guided these researchers towards curing the pandemic.
The virus was engineered by Cassiopeian partisans and released deliberately as a biological weapon inflicted upon Terran colonists. After an assault on the guerrilla headquarters in late August, information on the virus' engineering was discovered that aided in synthesizing a vaccine. The vaccine was put into experimental use by the middle of September and began mass production in late September. Once the disease was no longer out of control, the crisis was declared over in early November. The lead scientists involved in the creation of the vaccine, medical polymath Dr. David McGrady and haematologist Dr. Seilon were immediately and widely lauded for their rapid success. Despite McGrady's suicide not long after the conclusion of the crisis, he shared the Nobel Prize in Medicine with Seilon for their work in ending the crisis.