Harmful organisms are usually introduced through ingesting raw vegetables, meats (mostly undercooked, especially pork), raw fish (sushi), or unclean water. Swimming in the ocean, lakes, ponds, or rivers can cause harmful organisms to enter the nose or mouth. Poor hygiene, lack of handwashing, and biting nails can introduce harmful organisms. Petting animals or allowing them to lick you can transfer harmful organisms. Traveling abroad can expose you to new harmful organisms. Molds are harmful organisms that can be inhaled in water-contaminated homes or buildings. Finally, there is evidence that parasites can be sexually transmitted.