A group of French tourists returned home from Turkey last fall with diarrheal illnesses, and two of them developed a life-threatening kidney disease linked to the foodborne pathogen E. coli.

Now French health officials have completed an investigation into this illness cluster and say the two women were infected with a strain of E. coli similar to the rarely seen bacteria that caused the devastating European outbreak linked to sprouts grown from Egyptian fenugreek seeds.

In findings released Thursday by Eurosurveillance, the authors say the two cases of hemolytic uremic syndrome (HUS) were caused by E. coli O104:H4, “genetically similar but not indistinguishable” from the E. coli O104:H4 outbreak strain in France and Germany last spring.

And they conclude this is “further evidence” that Shiga toxin-producing E. coli (STEC) serogroup O104 circulates in Turkey, along with Afghanistan, Egypt and Tunisia. “Public health authorities and clinicians should be vigilant for possible STEC O104 infection in individuals returning from these areas who present with post-diarrhoeal HUS,” the article advises.

The study involved eight out of 22 French tourists who became sick after a two-week bus tour of Turkey in September of 2011. Two of these patients, both women in their 60s, experienced more serious illnesses, and upon their return to Caen, France they were treated for HUS, a complication of E. coli infection that leads to kidney failure.

Exposure to the bacteria most likely occurred in Turkey, the authors say, because the women began experiencing symptoms 11 days into their trip, and the average incubation period for E. coli O104:H4 is only 8 to 9 days. The incubation period is the time between contact with a pathogen and when symptoms begin to appear.

Evidence suggests that the six other sickened tourists also contracted their illnesses in Turkey, because none reported eating foods in common before their flight to Turkey, and there was no commonality between the meals they selected on the flight (out of a choice of two).

The two HUS cases may have been unrelated to the diarrheal illnesses of the other tour group members, according to the article.  

“The reported incubation period [for the other 6 diarrheal cases] was much shorter than that of the HUS cases,” it states. “Moreover, none were confirmed as STEC O104:H4 infection. Thus, this cluster may have been due to another pathogen and may have been a distinct event not linked to the HUS cases.” 

This most recent outbreak of E. coli O104:H4 from Turkey adds to evidence suggesting that the serogroup E. coli O104 circulates in this region of the world, says the report. Between 2006 and 2010, the authors note, there have been reports of travelers returning from Afghanistan, Egypt, Tunisia and Turkey infected with various strains of the serogroup.

In this case, the source of the infection could not be determined. The tour group’s meals were often served buffet-style, and investigators were unable to identify a specific food that might have been associated with illness. No member of the group recalled having eaten sprouts before or during the trip to Turkey. 

The report was written by members of the French Institute for Public Health Surveillance, the National Reverence Center for Escherichia coli and Shigella and the University Hospital of Caen’s Nephrology Department.