Health officials also shopped for grocery-store cantaloupe before pinpointing a single farm in Holly as the source. The Denver Post (http://bit.ly/p1bXaU) reports state epidemiologist Alicia Cronquist thought it slightly odd when she learned two people were sickened by listeria bacteria within days.
When two more reports arrived at the state health department in late August, Cronquist figured she was dealing with an outbreak.
"That was more than we would expect. That was concerning," Cronquist told the newspaper. "Clearly, we were on high alert."
Two more cases were reported the next day and three more the next day.
As of Thursday morning, the Centers for Disease Control and Prevention had confirmed that at least 55 people in 14 states have been sickened from eating cantaloupes, and eight have died.
Doctors and labs are required to report every case of listeria to the state health department.
In the early stages of Colorado's investigation, county health authorities used 15-page questionnaires to interview patients and their families about what they ate and where they bought it.
"The vast majority of people are elderly," Cronquist said. "The average age is in the 80s and they are quite ill. Their family members are at their bedside, and we are asking them to remember food that they ate a month ago. They are actually very difficult interviews."
Meanwhile, the bacteria in patients' blood was isolated, and state microbiologist Hugh Maguire's labs deconstructed the DNA profiles to see whether they had listeria strains in common.
Those profiles were uploaded into a CDC database of data from across the nation.
One of Cronquist's samples came from 84-year-old Herb Stevens Jr., who woke up shaking uncontrollably Aug. 22. His wife, Elaine, thought it was a cold until Aug. 24, when Herb's temperature reached 102.7 degrees and he couldn't stand, The Denver Post reported.
Scientists pulled food from patients' homes, including typical listeria suspects like deli meats, hot dogs and dairy products.
By Sept. 2, the state food lab determined that two patients had matching strains and two other patients matched in a separate strain. With hundreds of strains of listeria, two or more can be on the same food.
Epidemiologists in patients' home counties interviewed the patients to look for patterns while the state health department faxed and emailed a listeria alert to doctors, hospitals and labs.
And the public received the first notice of an outbreak: a warning for the elderly, the pregnant and those with compromised immune systems to avoid deli meats and unpasteurized cheese.
Cantaloupe wasn't mentioned.
By then, other states were reporting listeria sickness.
When Cronquist checked a CDC database tracking foods that listeria victims reported eating, she found that all the patients she was tracking had eaten cantaloupe.
Health authorities purchased 15 cantaloupes at three grocery stores and tested the rind and flesh for listeria bacteria. They also were testing patients' leftover melon. Maguire's lab fast-tracked the genetic matching, setting aside some of the lab's other, more routine work.
A week after the first public warning, health authorities announced they had linked the source of the poisoning to cantaloupe.
As more patient blood samples arrived at the state lab, they fell into three distinct strains. Cantaloupe taken from patients' refrigerators had the same strains but no sticker naming the farm.
In interviews, though, patients volunteered that the cantaloupe said `Rocky Ford' on it or was extra sweet.
On Sept. 12, the CDC told people not to eat cantaloupe from the Rocky Ford area of southeastern Colorado.
As the food tracking continued, Tri-County Health investigators collected receipts to track what food the Stevens family had bought over the last month, plus grocery store loyalty card information, so they could check purchases.
By tracking the melon purchases of patients back to the distribution trucks, investigators from the state and the Food and Drug Administration narrowed the focus to two farms and sampled soil and machinery.
Two days after warning people not to eat Rocky Ford cantaloupe, health officials announced they had pinpointed the farm.
Jensen Farms in Holly recalled its cantaloupes Sept. 14, while farmers in the Rocky Ford region miles away lamented how their produce was swept into early warnings about cantaloupe.
The Stevens family, who are wondering how they will pay for the care Herb Stevens needs just to walk and eat, has joined in lawsuits filed over the melons.
Investigators are still trying to determine how the Jensen Farms cantaloupe became contaminated.
"There is still lots to be known about this outbreak," said Chris Urbina, executive director of the state health department. "We still have lessons to learn out of this."
(Copyright 2011 by The Associated Press. All Rights Reserved.)