(July 24, 2:30 p.m.) Here is a look at some of the significant developments in the Salmonella Saintpaul outbreak that has been linked to fresh produce:

April 10 — First reported onset of illness date.

May 22 — New Mexico Department of Health notifies the Centers for Disease Control and Prevention that is has an outbreak of 20 cases of salmonella, and at least seven are confirmed as Salmonella Saintpaul. Public health officials are alarmed by the number of cases of the rare strain, which typically affects 400 people a year nationwide.

May 23 — More cases of Salmonella Saintpaul are identified in other states, most notably in Texas.

May 30 — The Food and Drug Administration becomes involved.

May 31 — New Mexico announces that an outbreak of 31 cases of Salmonella Saintpaul in that state is likely caused by fresh tomatoes. Traceback investigations begin.

June 2 — FDA advises consumers in New Mexico and Texas not eat roma or round, red tomatoes. Cherry tomatoes, grape tomatoes and tomatoes on the vine are not implicated.

June 5 — The FDA releases its initial list of growing areas not associated with the outbreak: Arkansas, California, Georgia, Hawaii, North Carolina, South Carolina, Tennessee, Texas, Belgium, Canada, Dominican Republic, Guatemala, Israel, The Netherlands and Puerto Rico are cleared.

June 7 — With 145 reported illnesses in 16 states, FDA expands its advisory nationwide, warning consumers not to roma or red, round tomatoes unless they are sourced from approved areas. Numerous retailers and restaurants respond by pulling the implicated varieties.

June 11 — Nineteen Florida counties are cleared by FDA, but some growing areas in the south and central parts of the state remain under investigation.

June 13 — McDonald’s begins to restock tomatoes from areas approved by FDA. Many other restaurants and retailers do the same.

June 14 — Baja California Norte is the first Mexican state cleared in the investigation.

June 20 — Twenty-seven Mexican states and Mexico City are cleared by FDA, but three other states remain under investigation. FDA investigators are dispatched to farms in Florida and Mexico, though FDA cautions that no growers have been implicated.

June 27 — Patricia Griffin, chief of the CDC’s enteric diseases epidemiology branch, says new illnesses continue to be reported, and contaminated product might still be entering the supply chain. She also says she is “keeping an open mind” about commodities other than tomatoes being a possible source of the outbreak.

June 28 — Western Growers asks the House Committee on Agriculture to have a hearing about the outbreak because “FDA and CDC have been unable to definitively determine the source or the cause.”

July 1 — CDC and FDA announce they are broadening the investigation to include “food items that are commonly consumed with tomatoes” but decline to say what other items are being scrutinized.

July 3 — CDC spokesman Glen Nowak clarifies the situation somewhat, saying that fresh salsa is under scrutiny.

July 5 — Multiple mainstream media outlets mistakenly report that the U.S. border has been closed to some Mexican produce imports. In fact, FDA has stepped up its sampling, causing some loads to be held while tests are pending.

July 9 — FDA issues a consumer advisory, warning at-risk consumers — infants, the elderly and people with compromised immune systems — not to eat fresh jalapeño or serrano peppers. Meanwhile, Coahuila is added to FDA’s list of approved shipping areas for tomatoes, leaving Sinaloa and Jalisco as the only Mexican states not on the list.

July 11 — The West Dundee, Ill.-based Perishables Group reports that retail tomato volume dropped 17% in June compared to June 2007. Movement of field-grown romas and red, round tomatoes suffers the most, falling 46.1%.

July 17 — Saying that tomatoes have not been absolved in its investigation but areas under scrutiny are no longer in production, FDA lifts its consumer advisory for the category. Meanwhile, CDC says the outbreak still is ongoing, but it appears to have reached a plateau June 10.

July 21 — A Mexican jalapeño pepper in a McAllen, Texas, warehouse tests positive for Salmonella Saintpaul. It is the first genetic match after eight weeks of traceback. FDA issues a more firm consumer advisory, warning all consumers nationwide not to eat fresh jalapeños or products containing the hot peppers. Retailers respond by pulling product from their shelves.

July 23 — CDC says there are 1,279 reported illnesses in 43 states, Washington, D.C., and Canada. There have been at least 239 hospitalizations. The most recent onset date of a reported illness is July 7.