Question

the lyme mystery
in the mid - 1970s, doctors were baffled when residents of lyme, connecticut, and neighboring towns developed a set of strange symptoms, including leg pain, swollen joints, and rashes. suspecting a reason beyond mere coincidence, a yale university research team systematically reviewed the cases. they discovered that all the victims had lived in wooded areas and that disease outbreaks had peaked in the summer and early fall, suggesting a connection to an insect. in addition, the number of cases occurring east of the connecticut river outnumbered those occurring on the west side. this information led to the hypothesis that the mysterious condition was related to deer ticks, since deer and the black - legged ticks they carry were more prevalent on the east side of the river. later research proved this hypothesis correct. the black - legged tick was found to carry bacteria that, when transmitted to humans through bites, cause the condition now known as lyme disease.
what is the main, or central, idea of the passage?
researchers discovered that a strange illness was caused by bacteria in the bite of the black - legged tick.
researchers discovered that a strange illness was more common east of the connecticut river than west of it.
because many victims lived in wooded areas, researchers suspected that a strange illness was caused by an insect.

Explanation:

The passage details how researchers investigated a mysterious illness in Lyme and neighboring areas. They found that the black - legged tick, prevalent in certain areas, carried bacteria that caused the illness. The main idea is about the discovery of the cause of the strange illness.

Answer:

Researchers discovered that a strange illness was caused by bacteria in the bite of the black - legged tick.