SANTO DOMINGO, Dominican Republic -- A mutated strain of polio traced to a vaccine has infected at least three people in the Dominican Republic and Haiti, causing the first cases of the disease in the Western Hemisphere since 1991, a regional health organization said.
"This is not a desperate situation from the view of outbreak control ... but it is still a surprise," said Pan American Health Organization spokesman Daniel Epstein on Sunday. The organization is part of the Washington-based Organization of American States.
The cases have been traced to the same oral vaccine that experts have used to eliminate the disease in many countries. Epstein said the standard vaccine still works against the mutated strain, and that health officials are organizing vaccination efforts in Haiti and the Dominican Republic.
Polio is a highly infectious disease that usually strikes children under 5. It damages the spinal cord and brain, causing paralysis and sometimes death.
The vaccine, known as Sabin 1 oral poliovirus vaccine, uses a weakened version of the virus to teach the body how to identify and fight active viruses.
None of the three patients had received the vaccine, and Epstein said doctors believe they caught the mutated strain from someone else. That person may have received a standard vaccination that mutated within them, then the person passed it on.
Scientists traced the cases back to the vaccine by an analysis of the polio strain, which shares 97 percent of its makeup with the one used in the vaccine, the health organization said.
In the Dominican mountain town of Constanza, where the first case was reported, hospital officials said they have been swamped by people seeking vaccinations.
"Everyone here is worried," hospital director Jose Matos Perez was quoted as saying in Listin Diario newspaper. "Everyone wants to vaccinate their children, including many with children that are over 5 years old."
Visitors to both countries should make sure they are vaccinated, the health organization said.
The last case of polio in the Americas was diagnosed in Peru in 1991.
The organization said tests had confirmed two cases in the Dominican Republic and one in Haiti since July. Doctors were investigating 16 other patients suffering polio-like paralysis. None of the patients has died.
The only other known case of an oral vaccine mutating into a virulent strain was in Egypt between 1983 and 1993, he said. More than 30 people were infected with that strain.
Source:Susannah A. Nesmith, Associated Press Writer