AUSTIN, Minn.  If you have to come down with a strange disease, this town of 23,000 on the wide-open prairie in southeastern Minnesota is a pretty good place to be. The Mayo Clinic, famous for diagnosing exotic ailments, owns the local medical center and shares some staff with it. Mayo itself is just 40 miles east in Rochester. And when it comes to investigating mysterious outbreaks, Minnesota has one of the strongest health departments and best-equipped laboratories in the country.

And the disease that confronted doctors at the Austin Medical Center here last fall was strange indeed. Three patients had the same highly unusual set of symptoms: fatigue, pain, weakness, numbness and tingling in the legs and feet.

The patients had something else in common, too: all worked at Quality Pork Processors, a local meatpacking plant.

The disorder seemed to involve nerve damage, but doctors had no idea what was causing it.

At the plant, nurses in the medical department had also begun to notice the same ominous pattern. The three workers had complained to them of “heavy legs,” and the nurses had urged them to see doctors. The nurses knew of a fourth case, too, and they feared that more workers would get sick, that a serious disease might be spreading through the plant.