Organism, Linked to Milk, Killed 14 in Massachusetts
Listeria monocytogenes, the bacteria that apparently contaminated the Jalisco brand of Mexican cheese, has caused four other outbreaks of disease in North America over the last 10 years. In 1983, the organism was responsible for 14 deaths in Massachusetts when it was found in pasteurized milk.
Listeria is often present in the guts of dairy animals and can be transferred to milk during the milking process, medical authorities say.
Dr. Shirley Fannin, associate director of communicable disease control for the Los Angeles County Department of Health Services, said the contamination can be passed on to consumer products such as cheese if the pasteurization process--which involves the heating of milk--does not kill all bacteria present.
In some cases, Fannin said, pasteurization is conducted improperly. In the Massachusetts case, however, an investigation found that the bacteria survived even though the process was performed correctly. The investigation concluded that the Listeria bacteria is highly resistant to heat.
Range of Illnesses
Once consumed through food products, Listeria can produce illnesses that range from mild nausea to fatal infections of the brain.
“Some people have a little discomfort and the disease subsides. With others, the organism invades the bloodstream and those people become very seriously ill,” Fannin said.
Most vulnerable to the extreme forms of the disease are those with immune deficiencies, such as newborn infants and their mothers, the very old or those already ill, Fannin said.
According to the Los Angeles County health agency, 45 of 71 cases recorded since April involved either infants or their mothers. Of the remaining 26 victims, 16 belonged to other high-risk categories.
The worst form of the disease, linked to the 28 recent deaths in Los Angeles and Orange counties, is known as meningoencephalitis. At that stage the bacteria has infected not only the bloodstream but the brain and the lining of the brain as well. Medical authorities say that people with such brain infections complain of nausea, headache and often fall into a stupor or coma.
Brain Damage Results
“Once it gets to the brain, it’s very hard to clear up,” Fannin said. “Even if you are successful, the people are usually left with brain damage.”
At earlier stages, however, listeriosis can usually be treated successfully with antibiotics such as ampicillin or gentamicin.
One of the problems of the disease, Fannin said, is its ability to move very fast from the simpler stages to more dangerous ones. Some of the recent victims died less than a week after the onset of their symptoms, Fannin noted. Incubation of the disease--the period from exposure to first symptoms--ranges from three days to two weeks.
Normally listeriosis is a rare disease, producing two to three victims per million population each year. On the average, 30% to 40% of the victims die, and most of those are members of the high-risk groups.
Medical Care Needed Only in Some Cases
It is not necessary for people who have eaten cheese that may be infected with Listeria monocytogenes to seek medical treatment unless they begin to show symptoms such as nausea, fever and severe abdomen pain and headaches, said Dr. Shirley Fannin, Los Angeles County’s associate director of communicable disease control.
“Some people who become exposed do not get ill at all,” Fannin said. “There is no need for alarm unless they have eaten the cheese and have those symptoms,” which usually appear anywhere from four days to two weeks after eating the product.
People who have consumed the cheese and who feel ill should contact a physician immediately, she said. The ailment can be treated with antibiotics.