Salmonella (cont.)

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How is Salmonella transmitted to humans?

Salmonellosis is spread to people by ingestion of Salmonella bacteria that contaminate food. Salmonella is worldwide and can contaminate almost any food type, but outbreaks of the disease have involved raw eggs, raw meat (ground beef and other poorly cooked meats), egg products, fresh vegetables, cereal, pistachio nuts, tomatoes, and contaminated water. A recent major outbreak (summer 2010) involved Salmonella-contaminated eggs from several U.S. producers that have caused the recall of over 500 million eggs (see the unusual causes section below). Another outbreak occurred in 2012 due to contamination of raw tuna ground up and used in sushi, sashimi, ceviche, and other preparations. The source (ground tuna termed Nakaochi Scrape) was from a processing plant in India. At least 116 people have been infected in 20 U.S. states.

Contamination can come from animal or human feces that contact the food during its processing or harvesting. New data about types of food contamination (food poisoning by Salmonella spp.) is available from the U.S. Centers for Disease Control and Prevention (CDC) or the FDA. Potential direct sources of Salmonella are pets such as pet turtles, dogs, cats, most farm animals, and humans that are infected or are carriers of the organisms. People and some animals who are carriers (like Typhoid Mary, described above) may never have symptoms but still shed the contagious bacteria in their feces.

Although typhoid and paratyphoid fevers can be transmitted by the same methods as salmonellosis listed above, the most frequent manner of transmission is by the feces of infected people contaminating the water or food source of uninfected people.

What are the risk factors for Salmonella infections?

The greatest risk factor for getting a Salmonella infection is ingesting the bacteria in food or water that has been contaminated with human feces. Another high risk factor for people in industrialized countries is eating raw foods (for example, unwashed fruit or vegetables) and drinking poorly or untreated fluids when visiting in a developing country where sources of food and drink may be contaminated. One common mistake is to assume ice cubes are safe and will not allow pathogens to survive in them. People whose immune systems are suppressed, young children, and the elderly are usually at higher risk to develop salmonellosis.


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