The greyness of your comment possibly indicates it has been deemed bigoted. It's relevant regardless. The subject of human parasitology certainly shows geographic and cultural distributions. One example is a strange case of neurocysticercosis, perhaps the most common cause of epilepsy and result of taenia solium or pork tapeworm. The case I recall involved a Jewish family, all infected and symptomatic. Doctors had difficulty discovering the source due to both assumed rarity of the disease and the preclusion of pork in a kosher diet. The eureka was the servant, who did not practice a kosher diet. Because this worm can lay 80k eggs per day, all of which are small and sticky, they tend to accumulate under fingernails, presumably as a result of grooming and outlier of hygiene. There are numerous parasites that are either or both geographically and culturally concentrated. In the US, neurocysticercosis is most common in California. According to sources not my own, this is due to the larger population of individuals who come from areas where swine handling is more common, along with certain mitigation practices or lack thereof. The French have a higher rate of toxoplasmosis, possibly due to, eg steak tartare. There are many examples.