The know-how, equipment and healers of Pern are different than the modern day medicine we know. In it's first five turns, the Telgar Plague was known as the "Gasping Death", and a less common name, "Holder's Death". Not until the plague spread from Telgar Hold to Telgar Weyr did the it take on it's new name, which remained even as it continued to migrate and traveled through Crom Hold, High Reaches Hold and High Reaches Weyr.
The Telgar Plague is believed to be a form of pneumonic plague. This claim was never confirmed with one hundred percent certainty, however, but is an educated guess based on many shared similarities. For one, the plague infested, attacked and destroyed lungs. Many symptoms, too, were similar, and included:
High Fever: Often fevers would rise to the point of delusions.
Weakness / Exhaustion: A constant or sudden lethargy that grew worse over time.
Headaches: Migraines that become more common than not.
Chest Pains: An ache in the upper chest, near the lungs, that ranged from severe to a dull sting.
Coughing: Further cause for chest pains and discomfort.
Trouble breathing: The final symptom.
Coughing was the first symptom, followed by fever, weakness / exhaustion, and headaches, with chest pains and trouble breathing following shortly after. It's victims would die gasping for air, hence the former name.
The most horrifying aspect of the Telgar Plague was how quickly it could strike, and more, how quickly it could kill. Within 24 hours, a life could be lost. Because the symptoms are so similar to less severe (but in Pern, still serious) illnesses such as the flu, the Holds and Weyrs were thrown into chaos. Only the bravest of souls dared to care for the sick. A child with a sore throat could easily be mistaken as one with the plague and left to fend for themselves.
Because the plague killed so fast and was easily mistaken for other health problems, it was very hard to study, even for those who dared to try.
The original source of the plague is still a mystery, and curiosity of the new generation has prompted individuals to seek out this information. Unfortunately, as turn after turn goes by, those details slip farther and farther away. Now, fifty turns later, most of the plague survivors were too young to recall many details or are now too senile in their old age.
The cure was discovered by a journeyman Harper named Yalin, who dedicated his life from his early teen years onwards to finding a cure. The remedy was a mixture of herbs, plants and reportedly, even some juices of Pern's fruits. The high demand and over-harvesting to aid the needed caused many of these resources to become extinct.
At age thirty, four turns after he had discovered the cure, Yalin died a sudden, still unexplained death.
The Telgar Plague, for reasons still unknown, did not effect dragons, watch-whers or firelizards. Yalin theorized it had something to do with their green blood, as other beasts (such as livestock) were effected, but critics argued his hypothesis was not sound. Again, nothing was confirmed. Perhaps, in time, a new Yalin will arrive to answer questions all else can only wonder.