GWEN IFILL: The government has launched an investigation into the deadliest outbreak of foodborne disease in more than a decade.
The Centers for Disease Control and the Food and Drug Administration say at least 13 people have died so far from listeria found in contaminated cantaloupes. Three other deaths are reportedly under investigation, and 72 people have been sickened.
Scientists have determined the tainted fruit originated at Jensen Farms in eastern Colorado. The melons were shipped to at least 25 states and some foreign countries.
And the number of reported infections is expected to rise.
For the latest on this story and what people need to know, we're joined by the director of the CDC, Dr. Thomas Frieden.
DR. THOMAS FRIEDEN, Centers for Disease Control and Prevention: Thank you.
GWEN IFILL: Why has this outbreak been so deadly?
DR. THOMAS FRIEDEN: Listeria is rare but deadly.
And, as you say, this is the outbreak that has, unfortunately, caused the most deaths in the past decade. Listeria affects particularly people who are elderly, pregnant women who may have a miscarriage or newborn infants, and people with weakened immune systems, people with diabetes or transplant patients who are on long-term steroids or cancer treatment.
DR. THOMAS FRIEDEN: Go ahead.
GWEN IFILL: I'm sorry. I was just going to ask, how does it spread? People think of cantaloupes as being pretty tough-skinned melons. How does it -- how does the disease get into the cantaloupe, and how does it get into the human being?
DR. THOMAS FRIEDEN: This is first time we have ever documented this particular bacteria, listeria, in cantaloupe.
And the Food and Drug Administration is currently doing an investigation at the farm to figure out why, so we can prevent future cases of contamination. But the skin, the flesh of the cantaloupe is actually a good place for bacteria to grow. Listeria is quite unusual as a bacteria for a couple of reasons.
One is that, once you eat it, it may be one to three weeks or even one or two months before you become ill. And that's the main reason we expect to see, unfortunately, case numbers rising in the coming weeks. And the second is that it's one of those rare bacteria that can actually grow even when it's refrigerated.
So as you put it in your refrigerator, most food, even if it's contaminated, you will knock down that contamination. But with listeria, the bacteria can continue to grow in your refrigerator, and that's why we tell people to throw out anything from Jensen Farms, any cantaloupe from Jensen Farms.
GWEN IFILL: Pardon me.
The source of the bacteria, this farm, was it farm equipment, farm animal, the soil itself? Do we know?
DR. THOMAS FRIEDEN: We don't know yet.
What we do know is that we're getting better at detecting this type of outbreak. Colorado is one of 10 states that the Centers for Disease Control and Prevention supports to track foodborne illnesses in real time.
And the state of Colorado did a terrific job. The cases were identified. They immediately investigated. They talked to people. It's not an easy investigation to do because it's a week or two or three since you have been exposed. And they quickly identified the source, were able to warn consumers, were able to work closely with us and the FDA to get the product off the shelves quickly.
GWEN IFILL: That's an interesting point, because when we have had previous outbreaks of E. coli or salmonella, it seemed like we spent weeks trying to find out what the source was.
DR. THOMAS FRIEDEN: This was done quickly. It was a combination of what we call shoe-leather epidemiology, doctors calling up, investigators calling up patients and asking, "What did you eat?" And then putting the pieces together to figure out what the source was.
And this is one of the things that we need to do even better in the future as our food supply gets more complex.
GWEN IFILL: We saw that these cantaloupes went to so many locations around the country. How -- if I have purchased a cantaloupe for my breakfast, how do I find out whether that cantaloupe is a problem?
DR. THOMAS FRIEDEN: If the cantaloupe in your refrigerator has this label on it -- that's the Jensen Farms label -- throw it out. If it has another label from any other company, we think at this point there is no evidence of any problem. It's OK to eat.
If it has no label on it, you can contact the supermarket or other place that you bought it and ask them if it came from Jensen Farms. When in doubt, throw it out.
GWEN IFILL: So if you call your supermarket or you go to your local farmers market and they don't know where it came from, you should just toss it?
DR. THOMAS FRIEDEN: Well, especially people who are elderly, pregnant women or people with weakened immune systems need to be particularly careful because listeria can be so dangerous and deadly for them.
GWEN IFILL: If you're not elderly, if you are in otherwise good health and you have no other kinds of immune problems -- immune system problems, does it just sicken you, but it's less likely to kill you?
DR. THOMAS FRIEDEN: It's less likely to cause serious illness. It may give you a fever, diarrhea or other illness, but it's unlikely to make you deathly ill, as it would to someone with a weakened immune system, unless you get a very high dose of it, unless you get a huge quantity.
And because it can continue to grow in your refrigerator, that's something that we are concerned about.
GWEN IFILL: Are we beginning to see more and more multistate outbreaks like this, or is this something which is unusual still?
DR. THOMAS FRIEDEN: In 2011, to date, we have already documented 12 multistate outbreaks of foodborne illness. This is partly a reflection of the increasing complexity of our food supply. It's also because we're doing a better job. We're tracking the genetic pattern of an increasing proportion of the foodborne illnesses that occur.
We're working with states and localities to identify rapidly when there are contaminations, so that we can stop them before they spread even further. Early this year, for example, we identified a cluster of very serious E. coli O157 infections from hazelnuts. We were able to stop that outbreak before it spread widely, because it was picked up so rapidly.
GWEN IFILL: We know of 13 deaths so far and 72, I think, illnesses. Do we expect these numbers to go up?
DR. THOMAS FRIEDEN: We know these numbers will continue to rise. Listeria takes a while to be diagnosed. It takes a while to develop.
But we do hope that people will check their refrigerator, and if they do have Jensen Farm cantaloupe, get rid of it so we can reduce the numbers in the future. And if you are someone who has a weakened immune system and do develop fever or flu-like symptoms, by all means, see your doctor, because antibiotic treatment is important and effective for listeria.
GWEN IFILL: Dr. Thomas Frieden at the Centers for Disease Control, thank you so much.
DR. THOMAS FRIEDEN: Thank you.