KNOWN FOR THE COMPLEX GEOPOLITICS. THANK YOU SO MUCH. >>> AS OF FRIDAY EVENING, THREE PEOPLE HAVE DIED IN THE WEST DUE TO THE HYSTERIA OUTBREAK LINKED TO BOAR'S HEAD DELI MEATS. ACCORDING TO THE CDC, THE LISTERIA OUTBREAK IS SICK AND AT LEAST 43 PEOPLE ACROSS 13 STATES . ALL OF THEM HAVE BEEN HOSPITALIZED. LAST MONTH, BOAR'S HEAD RECALLED 7 MILLION POUNDS OF DELI MEATS AFTER A LIVERWURST SAMPLE COLLECTED IN MARYLAND TESTED POSITIVE FOR LISTERIA. THE RECALL INVOLVED 71 DIFFERENT TYPES OF DELI MEATS SOLD BETWEEN MAY 10 AND JULY 29. FOR MORE ON THIS, CBS NEWS CHIEF MEDICAL CORRESPONDENT JON LAPOOK JOINS ME NOW. THANK YOU SO MUCH FOR BEING HERE. FIRST OF ALL, WHAT GROUPS ARE MOST AT RISK? ARE SOME PEOPLE MORE AT RISK THAN OTHERS? >> I JUST GOT OFF THE PHONE WITH THE CDC. THEY WANTED TO EMPHASIZE IT IS PEOPLE WHO ARE OLDER, SAY OVER 65, PEOPLE WHO ARE IMMUNOCOMPROMISED MIGHT HAVE COMPROMISED IMMUNE SYSTEMS, OR PEOPLE WHO ARE PREGNANT. THOSE ARE THE PEOPLE WHO ARE MOST AT RISK. MOST OF US HAVE IMMUNE SYSTEMS THAT CAN HANDLE THIS. LISTERIA IS UBIQUITOUS. WITHIN THE SOIL AND WATER IN DECAYING VEGETABLES. WE MAY BE EXPOSED TO IT AND HAVE SELF-LIMITED SYMPTOMS OF MAY BE DIARRHEA OR NAUSEA AND VOMITING, BUT WE CAN GET OUT OF OUR SYSTEMS OURSELVES. WITH IMMUNOCOMPROMISED PEOPLE, NOT ONLY GETS INTO THE INTESTINAL TRACT AND INTO THE BLOODSTREAM. ONCE IT IS IN THE BLOODSTREAM IT CAN GO TO THE HEAD AND CAUSE ENCEPHALITIS AND MENINGITIS AND PEOPLE CAN GET REALLY SICK. OF THE 43 PEOPLE WHO HAVE BEEN AFFECTED, THERE HAVE BEEN THREE DEATHS AS OF FRIDAY. >> HOW DO THEY EVEN DISCOVER THIS? A LOT OF THE SYMPTOMS YOU ARE MENTIONING COULD BE ANYTHING, RIGHT? >> IT IS KIND OF FASCINATING. IT IS LIKE MICROBE HUNTERS, BACK IN THE END OF MAY SOMEBODY GOT SICK. AS ALL THESE CASES START, IT STARTS WITH THAT CASE REPORT, THAT FIRST PERSON NEEDS SOMETHING, GETS SICK, AND I HAVE THE FDA, THE CDC AND THE USDA, UNITED STATES DEPARTMENT OF AGRICULTURE, ALL TRYING TO FIGURE OUT WHAT DID YOU EAT AND WHEN DID YOU EAT IT. I DON'T EVEN REMEMBER WHAT I HAD THIS MORNING FOR BREAKFAST AND THEY HAVE TO GO BACK AND MAYBE SOMETHING THAT IT A FEW DAYS AGO. THEN THEY TRACED IT. THEY WERE REAL DETECTIVES. THEY FOUND OUT THAT THERE WAS A POSITIVE CULTURE IN AN UNOPENED PACKAGE OF DELICATESSEN MEAT THAT HAD LIVERWURST. ONE IN MARYLAND, ONE IN NEW YORK, AND THEY SAID WHERE DID THIS COME FROM. BOOM, THEY TRACE IT BACK TO THE FACILITY IN VIRGINIA AND THEY DID THE RECALL. >> WHAT ARE THE ACTUAL SYMPTOMS FOR PEOPLE, BECAUSE THEY MIGHT HAVE SOME OF THE SYMPTOMS YOU JUST MENTIONED. HOW IS IT DIAGNOSED? >> THE WAY IT DIAGNOSED, IT'S VERY INTERESTING, BECAUSE THE TIP OF THE ICEBERG IS WHAT WE ARE SEEING RIGHT NOW. PROBABLY A LOT MORE PEOPLE TO GET INFECTED, THOUGH IT IS NOT ONE OF THE MORE COMMON INFECTIONS FOR GASTROENTERITIS, BUT WE MAY NOT KNOW ABOUT IT. WHEN WE KNOW ABOUT IT IS WHEN SOMEBODY GETS REALLY SICK AND WHEN THEY GET REALLY SICK IT'S WHEN IT GOES INTO THE BLOODSTREAM ANSWERS AFFECTING OTHER PARTS OF THE BODY. THE WAY THEY DIAGNOSE THAT TO BE THROUGH A BLOOD CULTURE, THROUGH A SPINAL TAP, THEY COULD SEE ABNORMALITIES IN THE SPINAL FLUID. AND YOU KNOW, IT IS A BIG DEAL, EVERYBODY IS HOSPITALIZED WITH THIS WHO GETS IT, AND THEY CAN BE TREATED WITH ANTIBIOTICS. >> IT IS JUST A COURSE OF ANTIBIOTICS? >> A COURSE OF ANTIBIOTICS. BUT YOU KNOW, THEY'VE TAKEN A LOT OF HEAT, THESE FEDERAL HEALTH ORGANIZATIONS. YOU HAVE TO HAND IT TO THEM. THEY GOT ON IT RIGHT AWAY. THERE ARE 43 CASES, WHICH IS A LOT, BUT ABOUT THREE TIMES THAT WAS WITH A CANTALOUPE OUTBREAK IN 2011, AND THERE WERE 33 DEATHS BACK THEN. YOU DON'T HEAR, YOU DON'T EVEN THINK ABOUT THESE ORGANIZATIONS AND WHAT THEY ARE DOING WHEN THINGS GO RIGHT, BUT WHEN THINGS GO WRONG, THAT IS WHEN THEY TAKE A LOT OF HEAT. I DO HANDED TO THEM. >> IN THE LAST 15 SECONDS OR SO, HAS THERE BEEN A RESPONSE FROM BOAR'S HEAD? >> I THINK THEY HAVE BEEN VERY RESPONSIBLE FROM WHAT I'VE BEEN READING IN TERMS OF DOING THE RECALLS, AND IN AN ABUNDANCE OF CAUTION ACTUALLY RECALLING THINGS ABOVE THAT. BUT REMEMBER, THE CDC IS SAYING LOOK, IF YOU ARE IN ONE OF THESE VULNERABLE GROUPS, THEN YOU SHOULD NOT EAT SLICED DELI MEATS OR EVEN ANY DELI MEATS, EVEN PREPACKAGED, UNLESS YOU PREHEAT IT TO 165 DEGREES FAHRENHEIT OR IF IT'S SEEMING HOT. MAKE SURE YOU LET IT COOL. AND FOR OTHER PEOPLE, OBVIOUSLY, THERE IS A RECALL NUMBER. I WANTED TO ADD THAT AND HAVE IT ON THE SCREEN. THE PREPACKAGED DELI PRODUCTS THAT SAY EST 12612 OR UNDER P