Yesterday the Union-Democrat reported that according to the Calaveras County Health Health Officer Dr. Dean Kelaita, six Calaveras County children diagnosed in recent weeks with E. coli have two different strains of the virus.
DNA testing by the state Department of Health Services shows that the first three children diagnosed in early May have the same strain. But the other three — all teenagers later found to have E. coli — have a different strain.
From the article:

A 13-year-old Angels Camp boy who exhibited cattle at the May 13-16 Calaveras County Fair was diagnosed June 11. Two brothers from Murphys, ages 14 and 17 who tested positive for E. coli were also exhibitors.
The DNA testing on the E. coli strain these three teenagers had closely matches the strain found in E. coli cases in Michigan, Missouri and Ohio, Kelaita said.
The first Calaveras County children diagnosed with the bacteria were Nicholas Kristoff and his 8-month-old sister Abigail. Nicholas, 4, of Angels Camp, developed an E. coli-related kidney complication called Hemolytic Uremic Syndrome and was sent to Oakland Children’s Hospital early last month. Nicholas was in critical condition for nearly three weeks, but has since recovered and is back home.
Soon after, another 3-year-old girl who received care from the Kristoff children’s mother, Staci Kristoff, tested positive.
All those children had the same kind of E. coli infection.