U.S. Health Officials Expect Significant Zika Cases in Puerto Rico, Other Territories

Federal health officials on Wednesday said the U.S. can expect to see a significant number of Zika cases in Puerto Rico and other U.S. territories where the mosquito that spreads it is likely to appear.

On the U.S. mainland, though, the virus’s impact is likely to follow the pattern seen by dengue, another mosquito-borne viral disease, Tom Frieden, director of the Centers for Disease Control and Prevention, told members of two House Foreign Affairs subcommittees in a joint hearing. The dengue virus has appeared in Hawaii, Florida and Texas but hasn’t been widespread throughout the country.

“We will see more cases among travelers to the U.S.,” Dr. Frieden said. “We will likely see significant number of cases in Puerto Rico and other U.S. territories.”

Chikungunya, another virus transmitted by the same mosquito as Zika, was detected in May 2014 in Puerto Rico, Dr. Frieden said, and by October 2014, it was found almost all over the island.

The experience shows that such viruses “can spread very rapidly in a population,” Dr. Frieden said.

He said Zika is expected to show up in places where dengue has been detected, and will probably appear sporadically in other areas as well.

President Barack Obama this week said he would ask Congress to approve $1.8 billion in emergency funding to combat Zika. Republicans, who control both the House and Senate, haven’t responded directly to his request yet, though some have said unspent funds allocated for fighting Ebola should be used to battle Zika and the mosquitoes that spread it.

Federal officials at the hearing pressed for more money and urged lawmakers to back the funding request.

Dr. Frieden said the agency has had to curtail some activities, such as dealing with Lyme disease, to reallocate resources to Zika. Some lawmakers showed openness to increased funding for the Zika effort.

“We need to spend some money on this,” said Rep. Curt Clawson (R., Fla.).

The Zika virus has become a major concern after Brazilian authorities linked it to complications including a rare birth defect called microcephaly, in which babies are born with dangerously small skulls and underdeveloped brains. The World Health Organization has declared possible complications from Zika a global health emergency.

The government hopes to begin Phase 1 of a trial of a vaccine against Zika by the middle of this summer, said Anthony Fauci, director of National Institute of Allergy and Infectious Diseases.

He said the government already has a “considerable amount of interest from pharmaceutical companies.” He said it could conceivably be possible to have a vaccine by the end of 2017.

But much about Zika is still unknown, federal health officials told lawmakers. Areas to be researched include transmission of the virus from a woman to her fetus, faster diagnostic tests to determine if an individual has been infected, and data on how long a man may harbor Zika in semen, health officials said.