Looking for One of the World's Most Dangerous
By GINA KOLATA
The New York Times
January 6, 1998
People in the United
States are sickened by their food once a year, on
average. But the food poisoning that suddenly appeared in
White City, Ore., in December 1981 was something else.
It was terrifying, and dramatic, and it seemed to have no
cause. In the end, however, that mini-epidemic turned out
to be the first show of force by a new strain of bacteria
that is now infesting the food supply, infecting as many
as 20,000 Americans a year and killing 500.
This is a scientific
detective story about those bacteria, known as E.coli O157:H7. It is a story that is continuing and that, in
the end, may lead to sweeping changes in the way food is
regulated in the United States.
The bacteria that puzzled scientists 16 years ago have
turned up in some of the most notorious food poisoning
episodes in recent history, including one involving Jack
in the Box restaurants in the Northwest in 1993 where
four children died after eating hamburgers and hundreds
of people became ill.
bacteria surfaced in 1996 in cases traced to contaminated
apple juice and lettuce, then dominated headlines last
August when 17 people in Colorado got sick after eating
hamburgers from beef processed by a Hudson Foods plant in
Nebraska. Hudson, based in Rogers, Ark., recalled 25
million pounds of its ground beef, the largest meat
recall in history, and the plant closed its doors.
Normally, Escherichia coli bacteria live innocuously in
the intestines of people and animals. But the new E.coli strain can cause diseases from standard diarrhea to
kidney failure and death. The bacteria still befuddle
medical doctors, who have misdiagnosed their infections
as everything from appendicitis to blocked blood vessels
of the colon.
Once someone is infected, there is no effective medical
treatment to combat the disease, and all doctors can do
is prevent dehydration, wait for the disease to run its
course, and hope for the best.
"I say the 'E' in E.coli stands for evil," said Nancy Donley, a
Chicago mother whose son, Alexander, died in 1993 from an E.coli O157:H7 infection.
In just four days, it "destroyed all of Alex's
internal organs and liquefied parts of his brain,"
Mrs. Donley said. It is, she added, "a terrible,
The search for the killer strain of E.coli began when
about a dozen people showed up one week in December 1981
in the emergency rooms of White City, a working-class
city near the California border. The patients described
terrifying symptoms: diarrhea attacks occurring several
times an hour accompanied by abdominal cramps that women
said were worse than labor pains and men said felt like a
hot sheet of metal had been placed on their abdomen. At
first, the patients said, they had watery stools, but
within hours, their diarrhea turned into what looked like
pure, bright red blood. And it lasted for days.
White City doctors tested patients' stools for a long
list of bacteria and parasites, but could not find a
culprit. It was not even clear whether the disease was
caused by an infectious organism, like a bacterium or a
virus, or whether it was due to a toxic chemical.
Finally, on a cold damp day in February 1982, frustrated
officials of the Oregon public health department called
in Dr. Lee Riley, who had recently begun work as a
medical detective for the Centers for Disease Control and
Prevention in Atlanta, and who is now a professor of
infectious disease and epidemiology at the University of
California at Berkeley.
Riley immediately flew to White City. "We figured
that whatever we were dealing with had to be completely
new," he said.
The first question Riley tackled was, What did the
patients have in common that their friends, family
members and neighbors did not? One clue was that they had
eaten at a local McDonald's restaurant.
Still, the association might have been purely
coincidental. And if the source was McDonald's food, it
was not certain what item was causing the illness. The
hamburgers? Unlikely, Riley reasoned. The meat patties
were cooked at such a high temperature, he said, that
"we couldn't believe that that kind of cooking would
allow a microorganism to survive."
While Riley dissected the Oregon cases, the disease
struck again, this time in Michigan in May 1982. Once
again, the patients had just eaten at a McDonald's
At the same time, working on the mystery disease at the
disease control centers, Dr. Joy Wells, a microbiologist,
noticed something suspicious. Nine of the 12 patients
whose stools were obtained at the start of the illness
contained a type of E.coli designated O157:H7, a label
based on the proteins found on the surface of that
strain. When the stool of healthy people was tested for
comparison, the strain was absent. But the medical
investigators were leery.
"We just didn't think E.coli could do something
like that," Riley said. It was possible that E.coli O157:H7 was a perfectly harmless bacterium that just
happened, by chance, to be in those patients' stools.
Finally, in July 1982, the investigators found what they
needed. A plant in Ohio that had supplied meat to the
McDonald's in Traverse City, Mich., had happened, as part
of its quality-control program, to have saved ground beef
from the suspected lot. Lurking in that meat was the same
strain, E.coli O157:H7.
out, Riley said, to be the smoking gun.
But if it was a common strain, it could well have been a
coincidence that the E.coli were in the patients' stools
and in the hamburger. So Dr. Wells began searching a
database of more than 3,000 E.coli samples that had been
stored for years at the disease control centers. Only one
was E.coli O157:H7. It had been isolated in 1975 from
the stool of a 50-year-old California woman who was a
naval officer in Oakland at the time.
"We tried to track down this patient," Riley
said, "but we couldn't find her."
He did, however, get her medical records from the Navy.
They showed that the woman had had a bloody diarrhea that
was identical to the diarrhea that struck the patients in
Oregon and Michigan.
Until then, said Dr. Patricia Griffin, who is a director
of epidemiology research at the disease control centers,
the case was shaky. "You could say, 'Maybe that's
just a nice bacteria that happens to be in food,"'
she said. But, she added, "finding that woman in
1975 who had had bloody diarrhea, and who had the same E.coli strain in her stool, that's when you start to get
chills." The researchers now knew that there was a
new strain of E.coli that could get into food and make
people seriously ill.
Yet a fundamental question remained. How, or why, did
these bacteria make people sick?
A crucial clue came from a seemingly unrelated
investigation that was going on at the same time. Dr.
Mohamed Karmali, who is the head of microbiology at the
Hospital for Sick Children in Toronto, had been tormented
over a mysterious illness. In 1980, in the space of 10
days, 14 children were admitted to his hospital, all with
the same symptoms. Their illness began with diarrhea.
About a week later, their kidneys failed. Two children
died and others were left with severe, permanent damage
to their kidneys and bowels.
Like Riley, Karmali
and his colleagues asked what these children had in
common. "There weren't too many leads," Karmali
said. "We were looking at all sorts of poisons and
chemicals." One hint, significant mainly in
retrospect, was that the children had visited a farm
market on the outskirts of Toronto and had drunk
unpasteurized apple juice.
"I was working day and night," looking for
infectious organisms that could have caused the strange
illness, Karmali recalled. "Then we had sort of a
break," he said. An 18-month-old boy died, and the
autopsy showed that the boy had E.coli bacteria in his
bowel that were making a potent, unidentified toxin.
Karmali began looking for the bacteria in the feces of
children admitted later with the kidney disease, called
hemolytic uremic syndrome, but could not find them,
probably because the children's active diarrhea had
So Karmali searched for the toxin instead. "To our
surprise, we found the toxin in the stool," he said.
Laboratory tests showed that the toxin killed monkey
kidney cells and a type of human cell grown for research.
That sounded familiar to Dr. Alison O'Brien, a
microbiologist at the Uniformed Services University of
the Health Sciences in Bethesda, Md., who heard about the
research at a scientific meeting. She worked with a
different bacterium, Shigella, that exudes a toxin with
exactly the same properties. It could be, she reasoned,
that the E.coli had picked up the gene that causes
bacteria to make Shigella toxin. If so, the new E.coli was armed with "a nasty little toxin," Dr.
O'Brien said -- indeed, probably the third most dangerous
bacterial toxin known, coming right after tetanus and
Dr. O'Brien examined the rogue E.coli, and sure enough,
discovered that it had somehow taken on the Shigella
toxin gene. Moreover, in many of the E.coli, that gene
was slightly altered in a way that made the bacterium
produce toxin even more deadly than the original toxin
made by Shigella.
No one knows exactly how the Shigella toxin genes jumped
to E.coli, but Dr. O'Brien has an educated guess.
Viruses that infect bacteria can sometimes pick up a gene
from one bacterium and carry it to another.
But if that was the seminal event, Dr. O'Brien said, it
probably did not occur in the United States, where
Shigella bacteria do not have the dangerous toxin gene.
Shigella in Central America do have that gene, however,
and in the 1970s, that area was hit with a pandemic of
Shigella dysentery. As the Shigella mixed with harmless E.coli in people's intestines, or as it mixed with
harmless E.coli that inhabited animal manure, a virus
may have carried Shigella toxin genes to E.coli. The
result would have been a strain that had never been seen
before: the toxin-armed E.coli O157:H7.
However the toxin does its work -- and scientists still
do not know for sure -- the result is that it can injure
cells that line blood vessels, plugging them with blood
clots. When this happens, the first symptom is bloody
diarrhea. But a small proportion of people, especially
young children and the elderly, develop hemolytic uremic
syndrome, the actual destruction of the kidneys that
occurs when blood vessels in these organs are destroyed.
The syndrome can lead to kidney failure or can be fatal.
Infections with E.coli O157:H7 are now the leading cause
of kidney failure in children, the CDC says, with at
least 1,000 children a year developing kidney failure
from these infections, and 3 to 5 percent dying.
Older people also tend to develop another complication,
thrombotic thrombocytopenic purpura, a sort of leakage of
the blood vessels that feed nerve cells. The result is an
encephalitis-like disease, with psychosis, comas or
The bacteria are surprisingly tough and virulent. For
example, said Dr. Marguerite Neill, chief of the division
of infectious diseases at Brown University School of
Medicine, most bacteria do not produce disease unless a
person is exposed to millions of them. But as few as 10
or so E.coli O157:H7 can produce illness -- far too few
to see or smell.
While most bacteria, including botulism bacteria, cannot
live in acidic environments, E.coli O157:H7 is
undaunted, able to grow in foods like unpasteurized apple
cider and commercial mayonnaise.
As researchers studied the organism and its effects, E.coli O157:H7 epidemics kept ticking away, usually going
unreported because they were sporadic and few doctors
thought to test for E.coli. But some outbreaks were hard
to miss. In September 1984, 34 out of 101 people living
in a Nebraska nursing home became ill with E.coli infections. They had eaten contaminated hamburgers.
In October 1988, 32 junior high school students from a
school in Minneapolis developed bloody diarrhea from
eating contaminated hamburgers in the school cafeteria.
Nonetheless, said Dr. James Marsden, a professor of meat
science at Kansas State University, "other than
among scientists, I don't think it really sank in what a
serious issue this was until the Jack in the Box
outbreak," in 1993, when four children died and
hundreds of people became ill.
meat of the new E.coli strain became "the biggest
challenge ever to face the industry," Marsden said.
Public health officials also changed their tack. The
Centers for Disease Control made a video about E.coli O157:H7 and sent it to public laboratories, suggesting
they look for the bacteria. Suddenly, the E.coli were
"We used to recognize outbreaks every couple of
years," said Dr. Griffin, the epidemiologist for the
Center for Disease Control. "Now we see 25 to 30 a
year." And the list of foods that caused outbreaks
keeps growing. "We look at that list and say,
'Wow,"' Dr. Griffin said.
But how, scientists asked, were the E.coli entering the
food chain? Because the first outbreaks seemed to be
associated with ground beef, scientists looked into
cattle and other farm animals.
Initially, the scientists came up empty handed. In 1982,
the Department of Agriculture could not find E.coli O157:H7 in any animals in the country, indicating that
the infected cows that contaminated the McDonald's
hamburgers must have been rarities. But now, said Dr.
Michael Doyle, the director of the University of
Georgia's Center for Food Safety and Quality Enhancement
in Griffin, Ga., as many as 1.5 to 5 percent of dairy
cows carry the organism. Dairy cows and other cattle seem
to be the Typhoid Marys of the epidemics, carrying the
bacteria harmlessly in their feces. From there, the
bacteria enter the food supply. In modern meat plants, a
single contaminated carcass can be ground up with scores
of other cows to produce hamburgers.
E.coli O157:H7 has also gotten into apple cider,
possibly because farmers fertilized their crops with cow
manure, Doyle said. It has also gotten into lettuce and
Other animals can carry E.coli as well. Doyle said he
helped investigate a case in Oregon where 11 family
members got sick after eating venison jerky. The deer had
been infected and the E.coli, he said, "survived
the brine process."
He added, "There are reports of kids who went to
petting zoos on farms and got sick from petting
The outbreaks have pushed the government into revamping
regulation of the food industry. Meat plants are starting
to replace the decades-old "sniff and poke"
system of inspection with high-tech microbial tests. The
Clinton administration is seeking greater power to levy
fines and order recalls.
and Drug Administration recently approved irradiation for
meat, a method that can kill E.coli. Non-irradiated
hamburger, safety experts say, should be cooked until the
inside reaches 155 degrees. They also advise thoroughly
washing produce and avoiding raw milk and unpasteurized
"I really credit the USDA and the FDA for new
initiatives," said Dr. Michael Osterholm, an
epidemiologist at the Department of Public Health in
Minnesota who in summer 1996 traced an outbreak that
sickened scores of children in a Twin Cities day-care
center to a cow carcass one child's family had in their
freezer. "But if you gave me all the money in the
world, I'm not sure I could keep these bacteria out of
the food supply."
That, however, is no excuse for complacency from
regulators or the food industry, Dr. Griffin said.
"The bottom line should be, is it reasonable that if
a consumer undercooks a hamburger that their 3-year-old
child dies?" she asked. "Even if only a small
number of children die each year, 50 or 100, I think it
galls consumers and that's understandable. They are
asking, Can't we have better control of how our food is