Plague riders

""Fourteen-year-old Shep Greenfield is a plague rider. He rides his horse between the makeshift colonies along the Wisconsin River, delivering homemade medicine to people infected with nightpox, a deadly, highly communicable disease. While trading meds for much needed grains, Shep finds evidence that suggests his parents--who disappeared in an attack a year ago--may be alive in a distant settlement called Dusty Hollow, where the nightpox is most prevalent. When he learns that the disease-ridden settlement is about to be burned down, Shep plots to find his parents"--Provided by pub."
"Shep Greenfield is a plague rider. When his parents disappeared after an attack on their home, he agreed to deliver medicine for the sinister Doctor St. John. The doctor runs the camp of River's Edge with cruelty and total control. But the pills he makes are the only hope people have, now that the doomsday plague, nightpox, has hit Wisconsin."@en