While browsing the Internet for medical lore, you happen on a medical encyclopedia article about purple spots disease.
Instances of purple spots disease have been documented in 150 countries. The disease affects one in every 100,000 individuals and there is no known cure. Individuals who have the disease remain completely asymptomatic until one day they very suddenly break out in purple spots that never go away.
Concerned that you may have purple spots disease and not know it, you scour the Internet and locate a reputable medical testing company that provides a screening test for the disease. The test is state of the art. It guarantees 99.5% accuracy, meaning that whether you have the disease or not, the result returned by the test will be correct 99.5% of the time. The test costs $300.00 USD to administer.
Figuring that your peace of mind is worth $300.00, you undergo the test for the disease.
Three weeks later, the results come back. The test is positive! You're advised to come in for a retest to be absolutely sure.
Based on the information above, should you be deeply worried? Why or why not?
Puzzlers are politely encouraged to place answers in spoiler blocks to avoid inadvertently spoiling the fun for other readers. :)