In 1903 something happened in yukon territory. it was coined "klondike fever," what was it?

1. the strange sickness swept through the territory and killed half the population
2. gold was discovered, people rushed to strike it rich in the gold fields
3. people left the area in large groups leaving it a ghost town
4. a cure was discovered for an illness in the yukon. the vaccine was able to kill off the illness completely.