SCATTERED EPIDEMICS IN THE UNITED STATES THIS PAST YE 3 SERVED AS A STARK REMINDER THAT NO NATION, HOWEVER RICH AND DEVELOPED, CAN EVER LET DOWN ITS GUARD AGAINST THE microbial world. In 1993 we found bacteria in our burgers, parasites in our water, and a deadly new virus in our resident mice. Diseases of deprivation, meanwhile, continued to exact a toll in many struggling countries, including our neighbor Cuba.
Trouble on the home front began on January 13 in the Seattle area. “We got a call from a gastroenterologist who had treated lots of kids for bloody diarrhea,” recalls Beth Vell, an epidemiologist with the Washington State Department of Health. Lab tests showed the children were infected with E. coli O157:H7, a particularly nasty strain of the common intestinal Escherichia coli bacteriun. By January 17 there were 37 diagnosed cases and, says Vell, “we’d identified a single risk factor associated with infection: eating a hamburger at a Jack in the Box restaurant.” The tainted meat was traced to five slaughterhouses in the United States and one in Canada.
Cattle frequently harbor this strain of E. coli in their intestines, apparently without harm. But sometimes bacteria spill onto meat surfaces during slaughter and become mixed into the beef whBn it’s ground. Unless this tainted beef is cooked until well done, the organisms may survive, multiplying in the gut of unsuspecting diners and producing a toxin that causes bloody diarrhea and painful abdominal cramps. In servere cases the kidneys fail.
Nearly 500 cases of the infection, including three deaths, were documented in the Northwest before the epidemic ended in February–the largest outbreak on record in this country. Jack in the Box has experienced no further trouble since it initiated tests for the bacterium and increased the cooking time for its burgers from two minutes to two and a half (until the meat shows no trace of pink). But the bug has struck again sporadically, sickening nine Sizzler patrons in Seattle in August, and six people from Butte, Montana, in October. To a void further food-borne illness, the USDA is revising meat inspection procedures; in the future all packages of raw meat sold to consumers may have to carry instructions for safe cooking and handling.
Anxieties about germs were compoundled when a waterborne disease devastated Milwaukee from mid-March to mid-April. On April 7 health officials traced the illness to high levels of a parasite called Cryptosporidium in water supplied by one of the city’s two water-treatment plants. Drinking water containing the .0002-inch-long creature–which is also commonly found in the gut of cattle–sickened roughly 370,000 people, almost a quarter of the metropolitan population.
“Some people got sick from a single sip of water at an airport fountion,” recalls Kathleen Fessler, an epidemiologist for the Milwaukee Health Department. About 41,000 people were treated for abdominal cramps and diarrhea, and more than 4,000 were hospitalized. Healthy people can rid themselves of the organism in seven to ten days. But if the organism is not checked by the immune system, it can cause prolonged diarrhea and life-threatening dehydration. The Milwaukee AIDs Project attributed the deaths of 54 patients to the parasite.
“The million-dollar question is how Cryptosporidium got into the water supply in the first place,” says Fessler. Sewage has been suspected, but a more likely source is agricultural runoff from dairy farms into the Milwaukee River. “Young calves are frequently infected with the parasite–the single biggest source of Cryptosporidium is their feces,” says Steve Gradus, lab director of the Milwaukee Health Department. “The Milwaukee River,” he adds, “runs through miles of dairy farms before emptying into Lake Michigan just north of the Howard plant” — the water-treatment plant that apparently failed.
In the normal course of events, explains Gradus, most contaminants are taken care of by the four steps of water treatment: coagulation, sedimentation, filtration, and chlorination. “if a coagulant does its job, it mops up foreign particles in the water and they drop to the bottom of the tank. The water then flows through enormous sand filters that trap most remaining impurities.” But the Howard plant had recently switched to a new coagulant, points out Gradus, and if it failed, the parasite and its tiny egglike oocysts could conceivably have slipped through the filters. To compound the problem, practical levels of chlorine don’t kill this particular parasite, and water plants at the time weren’t required to test for it.
STILL, WITH THE BENEFIT OF hindsight, it was easy to spot signs of impending trouble that might have tipped off city officials but went unheeded. The Milwaukee Water Works didn’t worry about the somewhat turbid water in late March, nor did it pursue consumer complaints about off-tastes, smells, and cloudiness. “We were in a state of denial,” said a Water Works spokesperson, because no one had been sick before. To prevent future outbreaks, the city has overhauled both its plants, introduced new particle and turbidity monitors, and begun testing for the parasite. Spurred by the Milwaukee epidemic, the Environmental Protection Agency is considering ordering new tests for pathogens in municipal water supplies this year.
The year’s most deadly new disease turned out to be yet another example of an animal microbe making an unwelcome incursion into humans. Early last June a string of suspicious deaths among Navajos and other Southwest residents was traced to a previously unknown type of hantavirus. Typically these rodent-borne viruses cause fever, shock, and kidney failure, sometimes ending in death. But this new-found strain attacked human lungs with a vengeance, more often killing the patient than not. Cases have since cropped up in 12 states, including Louisiana, Idaho, and Montana. By fall, 60 cases had been reported.
Quick detective work soon established that the viral culprit was carried by the common deer mouse–and probably had been for ages. So why did it suddently surface in humans in the Southwest last spring? Some New Mexico ecologists linked the outbreak to recent wet weather, which produced bumper food crops for mice, and a sudden mouse population explosion. A 20-fold increase in the number of deer mice may have furthered their opportunities for contact with humans.
Nothing in the United States, though, compared with the public health worries in Cuba, once a beacon of medical care in the developing world. Ironically, while U.S. health officials fretted about foodborne illness, their Cuban counterparts faced an epidemic of neurological problems linked to drastic food scarcity. The ailment, which causes partial vision loss and sensory nerve damage, first made spotty appearances three years ago, but cases rose to 500 a week by early 1993, and a nearly 4,000 a week by April, at the peak of the epidemic. More than 50,000 of the island’s 11 million residents have been affected.
At first physicians suspected a viral infection, but the outbrek’s timing soon suggested a nutritional deficiency. The puzzling symptoms began to appear after the collapse of the Soviet Union in August 1991, which ended aid to Cuba. Cubans were reduced to a stark diet of rice and beans, with “virtually no meat and about one egg a week,” reports Michio Hirano, a neurologist at New York’s Columbia College of Physicians and Surgeons, who examined patients in Havana. A lack of meat and dairy products leads to deficiencies in B-complex vitamins. Hirano adds that in Cuba these vitamins were already in short supply because the flour and bread aren’t vitamin enriched.
There was other suggestive evidence, too. Smokers and drinkers, who have a greater need for B vitamins, were the first to get sick. Children, pregnant women, and the elderly, who received more food, rarely fell ill. The Cuban syndrome, furthermore, resembled known vitamin B deficiencies such as beriberi, as well as suspected cases on historical record. In Jamaica in the 1880s, Strachan’s disease caused dimness of vision, numbness, and burning sensations in patients’ extremities; a similar syndrome cropped up among POWs during World War II. In any case, when Cuban patients were treated with B-complex vitamins, more than 60 percent improved in three weeks.
Hirano speculates that the disease arose because vitamin B deficiency interferes with the supply of energy to nerve cells. B vitamins are essential for the normal function of mitochondria (the cells’ “batteries”). “Nerve cells have big energy needs,” he points out, “and they seem particularly susceptible to nutritional deficiencies.” Hirano thinks a genetic susceptibility–say, mutations in mitochondrial DNA-many explain why only some people fall ill when food shortages are so widespread. Perhaps nutritional insult is adding to existing DNA injury.
Fortunately such questions are receding in importance. Since the government began distributing multivitamin pills to all Cubans at the end of May, the disease has sharply waned: by the end of September, new cases had fallen to one or two a week.
COPYRIGHT 1994 Discover
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