ST. CROIX — Puerto Rico, a U.S. territory of 3.5 million people, has become America’s front line in the Zika virus battle — the Centers for Disease Control and Prevention has sent 40 health workers to help Puerto Rico — as the virus, which has already infected at least 117 residents, is expected to increase dramatically and poses a threat to the U.S. mainland.
Puerto Rico, like the U.S. Virgin Islands, has a tropical landscape that is the ideal breeding ground for the mosquito-borne disease. Officials there have barred local blood donations, accelerated efforts to eradicate the Aedes aegypti mosquito that causes Zika, as well as dengue and chikungunya, and are trying to monitor every pregnant woman on the island due to fears Zika might cause a birth defect that causes babies to be born with misshappen heads. The voluntary registry by the C.D.C. extends to all Zika-infected women and their babies throughout the United States.
Puerto Rico’s governor has declared a state of emergency, placing a freeze on the price of condoms and products needed to curtail the spread of the disease, according to government officials. And the C.D.C., which earlier urged pregnant women to reconsider visits to Puerto Rico, has asked Congress for $250 million in emergency aid to battle Zika on the island.
“For the U.S., it really is the territory that is going to have the most infections,” said Steve Waterman, head of the C.D.C.’s dengue branch in Puerto Rico. “It has the best medical and public health infrastructure to try and answer some of these questions at the same time that we’re trying to control the disease.”
Among the C.D.C.’s main goals is to test every pregnant woman in Puerto Rico for Zika and prevent pregnant women from contracting the virus. The C.D.C. is urging people to take preventive measures.
Zika causes headaches, fever and a rash, though most people with the virus never show symptoms. C.D.C. researchers in Brazil and Puerto Rico are trying to determine whether the virus can cause microcephaly, a condition in which babies are born with abnormally small heads, and a rare paralyzing condition, Guillain-Barre, which can be fatal.
Among the 117 people who have tested positive for Zika in Puerto Rico, five were pregnant women. And at least five people have been hospitalized, including a man recovering from Guillain-Barre.
Mr. Waterman said more than 20 percent of the island population could contract Zika in an outbreak that could peak by summer.
“Our objective is to protect as many pregnant women as possible and that is what we are trying to do,” he said.