Final answer:
Ralph contracted his illness through fecal-oral transmission after drinking contaminated water, which is when pathogens from feces enter a new host through ingestion.
Step-by-step explanation:
Ralph was very sick after drinking contaminated water during a camping trip. His doctor said that he contracted the illness through fecal-oral transmission. This type of transmission occurs when pathogens in feces from an infected host enter the mouth of a new host, typically through contaminated food or water. Diseases like cholera, gastroenteritis, and certain helminth infections are spread this way. These pathogens can be present in feces and may include bacteria, viruses, and protozoa. In regions with inadequate sanitation measures, drinking water can become contaminated and lead to waterborne diseases. It was due to Ralph's consumption of water that wasn't treated properly or was contaminated with fecal matter.