A History of Salmonella

(The Washington Post)—The unfolding story of how Salmonella bacteria infected two giant egg operations in Iowa this summer is the latest chapter of a mysterious narrative about how a minor bacterial annoyance took off 35 years ago to become the second most common cause of foodborne illness in the United States.

Like the things that cause AIDS, Lyme disease, Legionnaire's disease and West Nile fever, the egg-loving germ (whose formal name is Salmonella enterica serovar Enteritidis) is a classic "emerging infectious agent." Sometimes called SE, it's a microbe that has been around a long time and has found a new or better way to reach its human victims.

For more than three decades, the strain of salmonella bacteria with a fondness for eggs has taken advantage of changes in this country's animal husbandry, food distribution and eating habits.

Along the way, scientists and public health officials have paid increasing attention to it, culminating recently in the Food and Drug Administration's 71-page "egg safety rule," which took effect in July. While the new standards may help reduce the problem, they are unlikely to eradicate it.

The problems in Iowa, from which about 1,500 people have gotten sick, hark back to the early days of the SE pandemic. (The bacterium's worldwide, near simultaneous resurgence starting about 1980 has earned that designation.)

"This current outbreak is like deja vu," said Christopher R. Braden, epidemiologist at the Centers for Disease Control and Prevention who is leading the Iowa investigation.

From the mid-1970s to the mid-1980s, SE infections increased sixfold in the northeastern United States. In 1986, a large outbreak in New England that was linked to stuffed pasta shells gave epidemiologists two crucial insights: All the illness was egg-related and traceable to a single source, a farm in Connecticut that provided the eggs used in the stuffing.

In addition, in the 1920s and 1930s, there was so much intestinal illness associated with duck eggs that that food -- once more popular than chicken eggs -- disappeared from the American table. There is good evidence that SE was the germ, one that would remain a low-grade threat for decades to come.

Read the full story by David Brown at The Washington Post