Understanding cause, symptoms of listeriosis poisoning in humans
As disease specialists investigate how four central Massachusetts people might have contracted a bacterial illness from milk, plenty of questions have arisen about the disease. Here are some answers.
Q. What is listeriosis?
A. It is a potentially lethal form of food poisoning caused by a bacterium called listeria that can travel in water, soil, or the intestinal tracts of animals, which can then excrete the germ into farmland.
Q. What food products are prone to listeria colonization?
A. Cheese, cold cuts, hot dogs, and deli meats have been identified as vehicles for the transmission of listeria to consumers. Milk can also harbor the germ but has rarely been identified as a source of outbreaks, in large measure because most milk is pasteurized, state authorities said. The bacterium thrives in the cold, so refrigeration won't stop it from replicating. Thorough cooking - including the pasteurization process - should kill listeria.
Q.How might listeria have entered milk products produced at Whittier Farms, the dairy implicated by state authorities in their investigation?
A. Specialists are still trying to figure that out. But Dr. Alfred DeMaria, the state's director of communicable disease control, said inspectors could find no evidence of problems with the pasteurizing equipment at Whittier's Shrewsbury plant. That made investigators curious about flavoring added during production, as well as about the tubes and pipes used during bottling.
Q.What are the symptoms of listeriosis and how easy are they to spot?
A. The signs of the disease, especially in its mild form, are strikingly similar to the aches and pains of influenza: fever, muscle discomfort, sometimes nausea or diarrhea. In more severe cases, patients develop headache, stiff neck, confusion, loss of balance, or convulsions. There is no easy test to diagnose the disease. Blood samples have to be drawn and sent to a laboratory that does sophisticated tests.
Q.How long does it take for symptoms to arise?
A. "The very difficult thing with listeria is that the onset of symptoms can range from three to 70 days after exposure," said Patricia Juliao, an epidemiologist at the US Centers for Disease Control and Prevention. "That makes it difficult, having that huge time period to monitor for symptoms."
Q. Who is most at risk of complications from listeriosis?
A. Like most infections, this disease strikes with particular ferocity against the elderly, newborns, and patients with underlying medical conditions. Pregnant women are also at risk of suffering miscarriages if exposed to listeria.
Q. What should consumers do if they think they have consumed tainted milk or other food products?
A. The risk of actually becoming ill, even if exposed to listeria, is quite low. Still, Juliao stressed the importance of being vigilant for symptoms; if they appear, immediately seeking medical care so that antibiotics can be prescribed.
Q. Can anything be done to prevent catching the disease in the first place?
A. Avoid unpasteurized milk. Cook beef, pork, and poultry thoroughly. Clean raw vegetables. Guidelines are even more stringent for people with impaired ability to fight disease. They should eat luncheon or deli meat only if reheated to the point of being steaming hot. They should also avoid brie, feta, and other soft cheeses unless clearly labeled as pasteurized.
Stephen Smith can be reached at stsmith@globe.com. 