All it takes to get a lifelong, unsuspected helminth infection is one food handler who has one and is a little careless about washing his hands after using the bathroom. Or a housemate -- same. Or one's mother -- same.
I got a liver fluke infection after one meal of sushi in a nice restaurant in Tokyo. I was there on business, eating at an hotel in the international-tourist district. It was all very snazzy and clean and the sushi was fresh as could be; just, alas, made partly from fish carrying microscopic trematode ova. And that was all she wrote. I found I was infected 15 years later when I went down like a brained calf with a massive gallbladder infection/blocked bile duct. I fortunately had a VERY responsible surgeon who refrained from the reflexive whacking out of my gallbladder nearly any other would have done based on my symptoms. And indeed I was passing something; just not a gallstone. I discovered what it was three days after being released from the hospital after they brought the acute inflammation down with IV Antibiotics and I finnished passing the obstruction. Which had been killed by electromagnetic radiation from the numerous ultrasounds and CT scans and nuclear imagings they did of my liver area, hunting for signs of Gallstones (which proved elusive, as I do not have them. I do have liver flukes). I identified the dead parasites in my stool because I happen to be an award-winning public-health journalist who also won a fellowship to study at the Centers for Disease Control 7 years ago. A very fine research institution, the CDC, and one which took care to stress that foodborne illnesses were a largely undiagnosed threat around the world that, until US doctors woke up to it, would certainly become endemic here. This is, after all, the jet age. It's not only "third world" countries that have endemic parasite problems (and we are more vulnerable than the natives, who have some genetic protection against infection we lack, just Europeans had genetic and acquired protection against smallpox that Native Americans lacked, and that had a kill rate of up to 100% when it was introduced to the New World. Well, something else is being introduced to the New World. By business travelers to Tokyo and Seoul and vacationers who visit Thailand and safari in Africa and scuba-dive in the Caribbean. You may never leave your armchair, but plenty of people do, for work or a hobby or simply the pleasure activity known as travel. And you cannot protect yourself from immigrants and business travelers and vacationers returning from abroad with a new load of unsuspected guests that will grow in their guts unsuspected indefinitely, and most certainly can be spread person to person -- the eggs are microscopic and can live for up to a year outside the body (& for 5 days even pickled in formalin solution -- that's formaldehyde, to you). I knew enough to know where to go to I.D. what I saw when I finally saw it, 15 years after I was infected (The CDC online parasiteImage Gallery is quite helpful, if anyone is interested); and how to get old colleagues from the CDC to do a proper lab workup after the inevitable failure of the local hospital's lab, which does lots of blood work but is completely untrained to identify parasites that aren't dressed in little worm costumes with neon blinkers reading, "No, it's not white rice; that would have been quite thoroughly digested, which is why you never see it in stool. Those are Tapeworm proglottids, as any public-health reseacher and no commercial lab tech knows. Stupid." (They don't wear such costumes, leaving it to slightly more alert people who know what a helminth infestation looks like that is, as is all too likely, secondary to a trematude infestation of long standing that thoroughly depressed the sick person's immune system for so long that the first busboy from south of the border with a Tapeworm infection HE didn't know about who was a little careless in washing his hands -- probably wasn't supposed to have taken 10 minutes in the bathroom to start with, need notwithstanding -- and then at some later time chopped the parsley on a salad eaten by immune-depressed diner, who then had Tapeworms as well as liver flukes. Oh, yes. And no OCD here. No thanks to the AMA -- US doctors are still trying to work out, like you, that the parasites don't have to swim here if we go to "third-world" places like, oh, Tokyo, for a major business deal, and -- gasp --- EAT while we're there. SUSHI.
How bizarre and improbable.
It happens. It has happened, and once it has happened, it keeps happening until all the people involved wake up and realize that the CDC and WHO and NIH are right and we nice clean white folks can get parasites right here in the US. Or, like my best friend's Dad, while serving in the Vietnam War. He came home with a Bronze Star, a Purple Heart, and two kinds of worm that it took years for him to get properly diagnosed (and that would not have been had he not gone to a VA hospital with some tropical medicine specialists on deck who know that vets of foreign wars are prone to be carriers of foreign foodborne illnesses. One does have to eat while abroad.
It is still happening, and it will happen again tomorrow.
Until the ignorant wise up, and cease spouting ignorance.
Go Google "public health parasitic infection epidemic." Or a reasonable subset thereof. The information and research is out there in plain sight. Get it between your ears before you speak on the subject again. It is the least you can do to not spread false rumors and, you know, hysteria. Like someone with a notable lack of any compulsion to check the most basic of his facts before he confidently announces their truth in a public-information forum. Some OCD would be good for you. Just as a balancer for irresponsible carelessness of public speech without regard to fact.