The deadly E. coli outbreak that swept Germany in May was caused by a virulent strain of the bacteria that produces Shiga toxin and is able to stick to the intestinal wall in a brick-like clumping pattern, according to two papers published last week. “Once you see it you will never forget it,” Helge Karch of the University of Münster, senior author of a paper in the Lancet Infectious Diseases, told the New York Times. The virulent strain caused haemolytic uraemic syndrome (HUS)–a blood clotting disease that leads to kidney failure–in 25 percent of the patients, a much larger percentage than previous outbreaks of Shiga-toxin–producing E. coli, suggesting that this strain is exceptionally virulent, a paper in the New England Journal of Medicine reported.
Other researchers argue there is not enough evidence to conclude the strain is particularly virulent. "In every outbreak we don't ascertain some mild cases, and in this one there's a large potential for underascertainment of a very large number of more mildly affected cases," Kirk Smith, supervisor of the Foodborne Disease Unit at the Minnesota Department of Health told CIDRAP News. So the high number of deaths may be attributable to an unusually widespread outbreak, not exceptional virulence.
In Germany, the daily numbers of reported cases have steadily decreased since they peaked on May 22, the World Health Organization reported today (June 27). To date, the outbreak has caused a total of 3,920 infections, including 48 fatalities.