It’s not just a 3rd world problem. Parasites and parasitic infections are common in humans, affecting millions of people worldwide. The World Health Organization (WHO) estimates that about 25% of the global population has an intestinal parasite infection, and in tropical and subtropical areas with limited access to sanitation and clean water, that number can be as high as 50%. In the United States, the CDC says that over 60 million people are infected with parasites.