Those lush grasses and eruptions of colorful spring wildflowers around the country this week may seem like a benign by-product of El Nino's drenching rains. But they could be a booby trap for outdoors-loving Americans. Ready to pounce out of the dense vegetation on any passing body will be another effect of the moist, warmer-than-usual weather: battalions of speck-size ticks carrying the summertime scourge called Lyme disease.
Although the number of new cases of Lyme seemed to have peaked in the U.S. at 16,000 in 1996, public health officials are warning that this year's total could soar. Since the first mysterious...