Bit by bit, gene by gene, doctors and researchers in Germany and around the globe are cobbling together a profile of the microbe responsible for Europe’s alarming outbreak of food poisoning.
Even as the grim toll climbed to 3,800 sick and 44 deaths, online articles in medical journals continue to shed light on the suspect bacteria known as E. coli O104:H4. And the authors appear to support the conclusion that the rare strain has properties that make it unusually toxic to its victims.
“Taken together, these data suggest that the pathogen in the current outbreak is exceptionally virulent,” concluded a team of German doctors whose article was published online this week by the New England Journal of Medicine.
However, health authorities in the U.S. continued to cast doubt on the staggering statistics coming out of Germany. While the epidemic has undoubtedly been unusual, actual statistics depend on how health authorities define and diagnose illnesses, and how many less-severe cases may have gone unreported.
Either way, the latest papers affirm previous reports that the German E. coli strain has the pathogenic traits of two previously known strains — a Shiga toxin similar to that of the more familiar E. coli O157:H7; and an ability to stack itself like bricks and cling to the interior surface of the intestine, thereby maximizing its ability to convey poison to its host.
Researchers explained that other toxic bacteria may adhere to intestinal walls, but less tightly and less densely, and yet other strains do not carry the Shiga toxins.
Scientists increasingly believe that these traits may explain why the outbreak that raged through the northern provinces of Germany appears to have been more deadly, with perhaps 25 percent of E. coli patients developing the complication called hemolytic uremic syndrome, or HUS. In previous outbreaks of O157:H7, fewer than 10 percent of patients develop HUS.
But that statistic is being questioned by U.S. epidemiologists, who suspect that the overall number of illnesses was probably far greater.
While illnesses are still being reported and treated in Germany and elsewhere, epidemiologists now agree that the outbreak began about May 8 in Northern Germany, reached its peak about May 23, and has been tapering off ever since. However, German health authorities reported four more deaths yesterday, and more are expected.
Other factors that emerge from this week’s publications:
— The great majority – 89 percent — of the HUS victims are adults, which is in stark contrast to the normal E. coli outbreak pattern, which usually targets children with weaker immunity.
— Women are overrepresented among case patients and especially among HUS cases, but it is unclear whether this is due to their greater exposure (i.e., they may have been more likely to consume the implicated sprouts) or the properties of the outbreak strain — or both.
— The majority of the HUS deaths are senior citizens, the median age being 74 years. However, they also include some younger adults and a two-year-old boy.
–The O104:H4 bacteria appears to have an incubation period of about eight days, which is twice the incubation period for E. coli O157:H7, the strain responsible for most serious E. coli outbreaks. If this is true, it means it could take longer for health authorities to detect an outbreak, aggravating their efforts to trace its source.
— Many patients appeared to be recovering from their initial cases of diarrhea, then reverted horribly, many of them eventually being diagnosed with kidney failure.
— Eurosurveillance, the online European journal of epidemiology, reported that doctors were observing “severe neurological symptoms, ranging from mild disorientartion and cognitive dissoc iation to stupor or severe, life-threatening seizures.” And patients experiencing such symptoms responded “weakly” to standard treatments for those symptoms.
— Unlike other toxic E. coli, which originate in cows or other ruminants, the O104:H4 microbe appears to have evolved in human hosts. And some epidemiologists have asked if the suspect sprouts could have been contaminated with human waste.
Meanwhile, Eurosurveillance, the online European journal of epidemiology, published two case studies from the outbreak. One was the case of a German woman in her 80s hospitalized June 1 in Munster, Germany, with intense abdominal pain and diarrhea. Surgeons removed part of her colon and monitored her condition for HUS. But, despite the severity of her illness, she has not been diagnosed with HUS.
In another case, a Dutch woman in her 30s contracted the illness while visiting the north of Germany, and was hospitalized in the Netherlands. Four days later, her condition lapsed into severe HUS. More recently, she has been recovering, but her 10-month-old child has come down with a secondary case which has caused seizures and kidney failure, leading to three weeks of kidney dialysis an uncertain prognosis.
Doctors believe the child was infected by the mother, who was suffering with diarrhea and had not been advised as to hygiene.
Cases of HUS have been reported from all of Germany’s 16 states, but with the exception of two clusters of illnesses linked to restaurants in eastern North Rhine-Westphalia and southern Hesse, the highest incidences of illness were from “the northern Germany outbreak area,” the New England Journal of Medicine reported. In those areas, centered around the city of Hamburg, “the outbreak has been almost simultaneous,” the NEJM stated, adding that most of the cases in other states were linked to travel in the outbreak area.
Meanwhile, the Centers for Disease Control and Prevention announced Thursday that a North Carolina resident is the fifth person in the United States to be confirmed ill with the outbreak strain of E. coli O104:H4 linked to German sprouts. The CDC said it is also investigating the death of an HUS patient in Arizona who had recently traveled to Germany.
Four of the five confirmed case patients — from Massachusetts, Michigan and Wisconsin, in addition to North Carolina — had been in Germany. A second case patient in Michigan likely has contracted a secondary infection, the CDC reported.