The British Columbia Centre for Disease Control announced last week that eggs were determined to be the source of a three-year increase in Salmonella cases in the lower mainland of the Canadian province.

According to a press release issued by the agency, over 500 cases of a particular strain of Salmonella have been reported since 2008.  Fourteen percent of infected individuals have required hospitalization due to the severity of their Salmonella infections.

“Eggs are the most likely source of this outbreak,” said Dr. Eleni Galanis, physician epidemiologist with the BC Centre for Disease Control.  “As sick individuals have eaten eggs from many sources, it’s not clear what type may be causing the outbreak. However, the investigation did uncover the use of ungraded and broiler hatching eggs in restaurants and other food service establishments in the Lower Mainland. Eggs used at these places were of poor quality, cracked and dirty.”

Most types of Salmonella live in the intestinal tracts of animals and birds. Prior to the 1970s, fecal contamination of eggshells was the primary source of Salmonella infection associated with eggs. In the 1970s, however, procedures for cleaning and inspecting eggs were implemented and the number of Salmonella infections associated with fecal contamination of eggshells is now extremely rare.

In the late 1970s and early 1980s, researchers discovered that Salmonella enteritidis has the capability to infect the ovaries of otherwise healthy hens and contaminate eggs before shells have formed.

Unpasteurized eggs should only be considered safe if they have been cooked to a temperature of 160 degrees Fahrenheit. Eating eggs prepared with a runny yolk is a risk factor for Salmonella infection. Undercooked egg whites and yolks have both been associated with Salmonella enteritidis infections.

The U.S. Centers for Disease Control and Prevention recommends following the below food safety procedures to prevent Salmonella infection from contaminated eggs:

– Keep eggs refrigerated.
– Discard cracked or dirty eggs.
– Wash hands and cooking utensils with soap and water after contact with raw eggs.
– Eat eggs promptly after cooking.
– Refrigerated unused or leftover egg-containing foods within 2 hours of cooking them. .
– Avoid eating raw eggs in foods such as homemade ice cream or eggnog. .
– Avoid restaurant dishes made with raw or undercooked, unpasteurized eggs, such as Caesar salad or hollandaise sauce.