the necessary vaccinations required to travel in El Salvador

close contact with someone who was ill on the return flight from El Salvador

the hike into the mountains and contact with ill residents

eating food and drinking beverages prepared in El Salvador

A client is seen in a clinic and diagnosed with giar- diasis. The client relates a history of just returning on a flight from El Salvador for a medical mission trip, eating food prepared by local residents at a farewell feast, and hiking into the mountains to reach ill residents during the medical mission. The nurse should conclude that the client most likely contracted the infection from: