Among bacteria causing significant diarrheal illnesses in the United States, Salmonella is second only to Campylobacter, causing an estimated two million illnesses annually.96 There are over 2000 different varieties of Salmonella (referred to as serotypes).
One of the most common serotypes of Salmonella is called Salmonella enteritidis. Each year this serotype causes many outbreaks where many people are infected from a common source. An annual average of 55 such outbreaks is reported to the Centers for Disease Control--a figure that undoubtedly underestimates significantly the number of occurrences. A recent well-publicized outbreak indicated that only three out of every 1000 cases are ever reported to public health authorities.97
Most victims develop an uncomplicated intestinal infection with diarrhea, fever, and chills, but over 10 percent of patients require hospitalization. Roughly three out of every 100 who are hospitalized die.98 Severe or life-threatening complications from infection with the Salmonella family of germs include: infection around the brain (meningitis), blood infections (sepsis), and chronic arthritis, with death resulting in some cases.99 Again, infants, the elderly, and those with immune system problems run the highest risk for severe disease.
Salmonella appears to freely cause large-scale outbreaks. One of the most striking single source outbreaks caused nearly 200,000 human infections. The whole epidemic was traced back to pasteurized milk produced at a single dairy plant.100 Another large outbreak that struck over 200,000 individuals was traced to infected commercial ice cream.101 The latter case highlighted the power of relatively few Salmonella organisms to cause serious disease. In spite of the thousands of people infected, public health researchers found that even the most contaminated ice cream specimens had only six Salmonella bacteria per half-cup serving of ice cream.102 The potential of such few numbers of bacteria to cause serious disease highlights the danger of these organisms and illustrates how difficult it can be to ensure their complete eradication from even a single food.
Other food items that have caused outbreaks of Salmonella infection include home made ice cream, chocolate, eggs, and products made from eggs. The egg situation has disturbed many consumers, because perfectly normal appearing grade A eggs can be infected. Even when the eggshells are completely intact and disinfected, Salmonella can still be residing inside. The reason for the Salmonella-inside-the-shell is that the bacteria can silently infect the egg-laying organs of apparently healthy hens. Since the shell is formed after the rest of the egg, the eggs can become Salmonella-infected before the shell even exists.103
Even in the highest risk region of the country--the U.S. Northeast--only about one in 10,000 eggs are infected with Salmonella. For this reason some consumers have felt that the risk from eggs is small. In the days of the family chicken farm that may have been true. However, in today's world of mass food production, risks are multiplied. The Center for Disease Control has pointed out that many dishes made in restaurants and commercial establishments use "pooled eggs." In other words, the contents of often hundreds of eggs are put together to make a huge batch of food. The CDC makes the following observation: "If 500 eggs are pooled, one batch in 20 will be contaminated and everyone who eats eggs from that batch is at risk."104
Another disturbing outbreak of Salmonella occurred recently in the western part of the country. At least 90 individuals became ill from eating contaminated beef jerky. Jerky thus joined a list that now includes sausage and salami as important disease-bearing agents. The reason this is so disturbing is that such animal products are typically considered "ready to eat." The average consumer sees no need to cook or sterilize these items.105 Chocolate also poses a concern since most of the time it is not heated prior to eating. A summary of the characteristics of Salmonella diseases is shown in Figure 18: Salmonella Diseases.
