There is some evidence that small subpopulations of clinical isolates are more capable of colonizing the heart throughout the course of infection, but cardiac manifestations are usually sporadic and may rely on a combination of bacterial factors and host predispositions, as they do with other strains of cardiotropic bacteria. Recent outbreaks
According to the Centers for Disease Control and Prevention (CDC) there are about 1,600 cases of listeriosis annually in the United States. Compared to 1996–1998, the incidence of listeriosis had declined by about 38% by 2003. However, illnesses and deaths continue to occur. On average from 1998 to 2008, 2.4 outbreaks per year were reported to the CDC.Some notable ones are listed below. 2002 United States outbreak
A large outbreak occurred in 2002, when 54 illnesses, 8 deaths, and 3 fetal deaths in 9 states were found to be associated with consumption of contaminated turkey deli meat. 2008 Canadian listeriosis outbreak
An outbreak of listeriosis in Canada linked to a Maple Leaf Foods plant in Toronto, Ontario killed 22 people. 2011 United States listeriosis outbreak
On September 14, 2011, the U.S. Food and Drug Administration warned consumers not to eat cantaloupes shipped by Jensen Farms from Granada, Colorado due to a potential link to a multi-state outbreak of listeriosis.
Complications
Complications associated with medullary sponge kidney include the following:

Kidney stones
Urinary tract infection (UTI)
Blood in the urine
Distal renal tubular acidosis (Type 1 RTA)
Chronic kidney disease (rarely)
Marked chronic pain

Cause
In recent studies, insight has been obtained on the genetic basis of this disease, supporting the hypothesis that MSK is due to a disruption at the ureteric bud-metanephric mesenchyme interface. This explains why so many tubular defects coexist in this disease, and particularly a distal tubular acidification defect of which the highly prevalent metabolic bone disease is one very important consequence. In addition to the typical clinical phenotype of recurrent stone disease, other clinical profiles have now been recognized, that is, an indolent, almost asymptomatic MSK, and a rare form characterized by intractable, excruciating pain. It was previously believed that most cases of medullary sponge kidney were sporadic; however, recent studies show familial clustering of MSK is common and has an autosomal dominant inheritance, a reduced penetrance, and variable expressivity. Other theories suggest that dilatation of a collecting duct may occur, caused by occlusion by uric acid during fetal life or resulting from tubular obstruction due to calcium oxalate calculi secondary to infantile hypercalciuria.A rare, autosomal recessive form is associated with Caroli disease. Diagnosis
Classically, MSK is seen as hyperechoic papillae with clusters of small stones on ultrasound examination of the kidney or with an abdominal x-ray. The irregular (ectatic) collecting ducts are often seen in MSK, which are sometimes described as having a "paintbrush-like" appearance, are best seen on intravenous urography.