At least four people in Humboldt County, CA, have been sickened with genetically linked cases of E. coli since July, according to a report by the Eureka Times-Standard. The first case appeared in July, the second in August, and then another two followed in October. The infections are being caused by a “very specific” strain of E. coli not found anywhere else in California, according to a public health official with the county’s department of health and human services. Officials have not determined a source after interviewing patients for common food histories. Investigators have asked local healthcare providers to send lab samples from anyone experiencing bloody diarrhea in an attempt to uncover more E. coli cases and possibly solve the mystery. Symptoms of E. coli infection include severe diarrhea, nausea and abdominal cramps.