Forty American tourists who were part of a group of 114 people became seriously ill during a stay in the Dominican Republic.
The Central Oklahoma Parrothead Association was vacationing in Punta Cana in April, staying at the Hotel Riu Palace Macao when a number of them were sickened.
Some of them lost up to 14 pounds because of the possible effects of a parasite.
The situation occurred in April, but was reported in recent days by the US media.
These cases are in addition to many reported in recent weeks in the Dominican Republic, including at least seven deaths of US tourists.