A hat tip to Dan Cohen of Maccabee Seed Co. for sending along a USA Today article by Elizabeth Weise that we think is a fascinating piece regarding the early days of the current Salmonella Saintpaul Tomato outbreak. The piece is entitled, How Modern Science and Old-Fashioned Detective Work Cracked the Salmonella Case:
…health officials say that because the first cluster of patients surfaced on the Navajo Nation in New Mexico, where they are served by a small, close-knit medical community, federal investigators were able to quickly identify the contaminated foods and take steps to contain the outbreak the past two weeks.
After being the first to recognize the signs of an emerging outbreak, the federal Indian Health Service staff played a key role in the search for the tainted food. “It was 21st-century molecular epidemiology and old-fashioned boot leather,” says John Redd, the infectious disease branch chief with the Indian Health Service in Albuquerque. “You’ve got to get out from behind your desk and hit the road sometimes.”
Kimberlae Houk has 24 years of experience in public health nursing in the Navajo Nation, the largest reservation in the USA, with lands extending into Arizona, Utah and New Mexico.
Her Shiprock Indian Health Services Unit provides medical care to more than 45,500 American Indians, mostly Navajo, in an area that covers 23 communities in the three states. Homes can be extremely isolated, and many are without telephones.
Houk knew something was up on Monday, May 19, when four people very sick with diarrhea, fever and abdominal cramps showed up at the Northern Navajo Medical Center in Shiprock, N.M.
“A lot of time with these kinds of diseases you get your babies and your grandmas in the hospital,” she says. “But in this one we had fit 30-year-olds. And we just don’t get 30-year-olds in the hospital with dehydration.”
And these people weren’t just dropping in at the doctor’s office. “We serve a very rural population. They have to drive an hour to the clinic and an hour back. So it’s a big deal to come in,” Houk says.
With previous experience with outbreaks of measles, whooping cough, hantavirus and even the plague, Houk immediately went into outbreak mode. “We literally drop everything when there’s a communicable disease, to protect people.”
That day, “We all just ran,” says Houk. “We can really get on top of things quickly because all our nurses, our doctors, our clinics, our labs, we’re all under the same roof.”
…Then New Mexico posted the genetic fingerprints of its cases onto PulseNet, the CDC’s computer disease-tracking network. Within hours, matches began to show up. The outbreak wasn’t just in New Mexico and Texas, it was all over the country.
Now came the challenge: What connected a patient on remote Navajo lands with the other patients throughout the nation?
Even though it was Memorial Day weekend, everyone mobilized to work. New Mexico, Texas, the CDC and the Indian Health Service began holding daily conference calls. As other states got patients, they joined in. New Mexico started the calls, but eventually CDC took over hosting them because they “can accommodate 100 people on their lines,” Houk says.
In a case like this, epidemiologists, the doctors who study outbreaks, pull out what they call a “shotgun survey.” It’s a long — in this case 22 pages — survey that covers just about anything a person might eat, drink or be exposed to that could cause such an illness.
“Shotgun, because it’s like shooting in the dark to see what’s there,” says Texas’ Gaul.
Enter the Indian Health Service again, charged with the task of administering the survey in the Navajo Nation, which by sheer chance seemed to have gotten the most cases in New Mexico.
“Our Indian Health nurses would drive two or three hours to try to find these people and when they couldn’t find them, they’d have to go back,” he says.
Also, each nurse had to painstakingly reconstruct everything their patient had eaten in the previous two weeks. “Nurses pulled out calendars for clients and said, ‘Where were you? Who were you with? What meal did you have with that event? What did you do before the event, and what did you eat later in the day?’” says Houk.
Not only that, but the surveys had to be given in three languages: English, Spanish and “English with Navajo clarification,” Redd says.
“The folks in New Mexico really did an amazing job,” says CDC’s Williams. “Extraordinary.”
By Saturday more than a dozen of these questionnaires were completed. Epidemiologists and public health workers pored over them, looking for patterns. Jessica Jungk, a master of public health who also helped track spinach in the 2006 E. coli outbreak, got called in to help analyze the data. But while tomatoes were high on the list of foods eaten, they weren’t a strong enough presence to be isolated as the problem.
Ettestad got on the phone with CDC’s Williams, who urged really zeroing in on what people were eating. “Get them to open their refrigerators, their pantries” while they talk, he suggested.
To do that, a nurse was sent into a patient’s home “and she literally pointed at every shelf on the refrigerator and every cabinet and asked, ‘Did you eat anything on this shelf?’ It’s a difficult thing to do. It makes people feel anxious,” Houk says.
But it did the trick. Even people who swear they didn’t eat raw tomatoes remember they might have when asked about salsa or guacamole or a slice of tomato on a hamburger. On Saturday, with surveys coming in not only from New Mexico but a few other states as well, the percentage of patients who’d eaten fresh tomatoes stood at 75%, compared with an average of 68% random Americans. By Sunday, with more cases analyzed, the share shot up to 83%, Ettestad says.
But that wasn’t enough to nail tomato as the culprit. Next came the scientific gold standard, a case control survey to look at whether people who didn’t get sick ate significantly less of the suspect food than people who did. For this, the investigators employed a tried and true tool for random selection: spin-the-bottle.
The key to a good case control is randomness. Investigators want to compare healthy people with those who got sick, but they want them to be similar in every other way, and they don’t want to bias who gets chosen. Today epidemiologists use computerized phone books and an Internet randomizing program.
But a lot of the people they needed to talk to didn’t even have phones.
So they want back to the old techniques. “You go out to the house of someone who got sick. You take a bottle and put it on the ground. You spin it and you go in the direction it points until you hit a house,” Ettestad says. “And that’s just as random as the Internet.”
Redd of the Indian Health Service didn’t even have a bottle: “I was spinning a government-issue pen.”
By Saturday, May 31, New Mexico was ready to start warning people. We felt we had enough evidence and we needed to protect our citizens,” Ettestad says….
Dan has been kind enough to share ideas with us here and here, and after the spinach crisis, he wrote for the Community Alliance with Family Farmers an intriguing proposal entitled, “The History, Politics & Perils Of The Current Food Safety Controversy” CAFF Guide to Proposed Food Safety Regulation.
It is a very interesting piece and, although much is controversial, Part II, entitled “A New Pathogen” (page 14) deals with E. coli 0157:H7 and discusses some of the same case/control and epidemiology issues that the USA Today piece deals with in relationship to the Salmonella Saintpaul outbreak.
What we find intriguing about this USA Today piece is that it demonstrates how, even in our high-tech times, much depends on individual motivation.
This case wasn’t discovered by a computer; the truth was wrestled from the ill by a highly dedicated group of health care workers. Really extraordinary work.
Many thanks to Dan for bringing it to our attention.
