Public-health officials have yet to pinpoint the source of an outbreak of infections from a rare strain of Escherichia coli that resulted in the death a 21-month-old girl in New Orleans, Louisiana, and has infected thirteen others. Details of an ongoing investigation by federal and state health officials were released in a 10 June statement from the US Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia. The organism behind the outbreak has been identified as part of the serogroup O145, which can produce a dangerous Shiga toxin.

One serotype, called O157:H7 (pictured),  takes the blame for most Shiga-toxin-producing E. coli (STEC) cases. O145, which requires more testing to identify, is one of ‘the Big Six’ — a group of half a dozen serogroups responsible for most of the STEC infections that don’t come from O157:H7. O145 infections can be treated successfully if antibiotics are administered in time.

According to the CDC, the investigation is looking at both food and non-food exposures, and state public-health officials are interviewing patients about what they ate or might have been exposed to before getting ill. Interviews with ten patients have produced no clear pattern, and it’s possible that the source may never be known. Dates of illness onset range from 15 April to 12 May. At this point, it’s impossible to be sure if the outbreak is over or poses further threat.

Beginning 4 June, the US Department of Agriculture expanded its raw-beef-product testing protocol to include the Big Six. From December 2011 to March 2012, another Big Six strain, O26, contaminated raw clover sprouts at a popular sandwich chain and infected 29 people.

Photo: CDC