ON JUNE 7, 2008, the U.S. Food & Drug Administration (FDA) issued a warning to American consumers that an outbreak of salmonella infection “had been linked to consumption of some raw red plum, red Roma, round red tomatoes and products containing these raw tomatoes.” And by early summer of 2008, the FDA had substantiated 887 cases of salmonella enteritis, inferentially associated with consuming certain varieties of tomato. The outbreak was centered in Texas and New Mexico. (There were no reported cases of enteritis from Rhode Island in the initial survey.)

Salmonella enteritis, it should be pointed out, is not that rare a clinical phenomenon. In an average year, the United States witnesses many thousands of cases. Still, government officials publicized this outbreak since they thought that its source was readily identified.

Salmonella is the name given to a genus of biologically related bacteria (some innocuous, some dangerous) that inhabit the gastrointestinal tracts of domesticated birds and animals as well as certain reptiles, such as turtles.

Two American scientists, Theobald Smith (1859-1934), a physician and experimental pathologist, and Daniel Elmer Salmon (1850- 1914), a veterinarian who founded the governmental Bureau of Animal Industry, a precursor to the FDA, were jointly studying the causes of a sometimes lethal cholera-like disease in domesticated swine. In 1885 they isolated a specific bacterium later named salmonella. Since then, other members of the salmonella genus have been shown to cause typhoid fever, paratyphoid fever and one species of salmonella called Salmonella enteriditis — the major cause of food poisoning in America and abroad.

The relationship between Salmon and Smith was strange and contradictory. On the one hand, their collaborative investigations yielded much scientific insight into the nature of enteric infection and the development of antibodies to these illnesses; on the other hand, there was much antagonism between the two.

Salmonella food poisoning (enteritis) is an acute illness characterized by an incubational interval of 12 to 18 hours, moderate fever, abdominal distress, diarrhea (usually non-bloody) and, in most cases, recovery within four or five days. The self-limiting illness tends to be more serious in three categories of humans: the nursing-home elderly, premature infants and those with immune deficiencies, such as those suffering from HIV infections or those undergoing extensive radiation therapy.

The germs causing salmonella food poisoning have clustered in the intestinal tracts of domesticated chickens; accordingly, the great majority of salmonella food-poisoning cases occur in those eating raw or undercooked eggs. These bacteria often contaminate the interior of the egg before its being encased by the shell; and therefore sterilizing solely the chicken shell may not affect the viability of the salmonella bacteria harbored within the egg. Adequate cooking of eggs, then, remains the most dependable means of preventing salmonella food-poisoning.

More recent epidemiological studies of recent cases of salmonella food poisoning now cast doubt that tomatoes were the sole, or even principal, source of the 2008 outbreak. Given the complexities of farming, harvesting, storage, distribution and retailing of a vegetable such as the tomato, the point of intimate contact between the pathogen and the vegetable carrier may never be determined to anyone’s critical satisfaction.

Whence came the tomato? It is one of many New World contributions to the cuisine of Europe, Africa and Asia. Some think that it originated in the highlands of Peru, but most agronomists now believe that the Aztecs began cultivating what had been a wild fruit. Indeed, its Aztec name is xitomatl.

Cortez conquered the Mexican city of Tenochtitlan in 1521 and the tomato plant soon found its way east across the Atlantic, first as an ornamental plant. By 1544 tomatoes entered into Italian cuisine, called pomi d’oro (golden apples). The transplanted tomatoes of the 16th Century are now assumed to have been the yellow cultivar, hence the name “golden.”

In France the tomato was called pomme d’amour (love apples) because of its alleged aphrodisiac quality. (Is there any food that has not been assigned aphrodisiac powers?) In Britain as well as the other northern nations of Europe, however, the tomato was viewed with deep suspicion as a poisonous plant (perhaps anticipating the science-fiction cinematic thriller of the 1960s, Attack of the Killer Tomatoes, because the tomato was biologically related to such toxic plants as deadly nightshade). It was not until the 19th Century that tomatoes were incorporated into the general diet of Germanic and English-speaking nations.

For a brief interval earlier this year, Americans ostracized tomatoes as though they had been dusted with anthrax spores. The average citizen, through his diet of pizza, salsa, tortillas, tomato soup, garden salads, ketchup and sundry other culinary exploitations of the tomato, now happily consumes over 38 pounds of tomatoes a year.

Stanley M. Aronson, M.D., a weekly contributor, is dean of medicine emeritus at Brown University ( smamd@cox.net).