Franco Ordonez

WASHINGTON: An obscure mosquito-borne virus that has already prompted warnings in Central America to avoid getting pregnant and is thought responsible for thousands of birth defects in Brazil has now reached the United States, according to health officials.

The Centers for Disease Control and Prevention said U.S. doctors should test newborns who show signs of the Zika virus, especially in states such as Florida, where mosquitoes are a daily nuisance. The advisory came the same day that Arkansas officials confirmed that they had diagnosed someone there with the virus and warned it was possible that the virus had infected the local mosquito population.

The dual announcements mark the latest twist in a burgeoning public health crisis that evokes memories of the 2014 Ebola crisis, when a slow international response to an unusually virulent outbreak of disease ended up costing the lives of thousands.

The threat from the Zika virus, which causes fever, rash and joint pain, is not so much to those who contract it, however, but to their unborn children, who often suffer from microcephaly, a birth defect characterized by an unusually small head and developmental problems. As many as 4,000 infants in Brazil are thought to have suffered the condition because their mothers had been infected with Zika.

Zika has already been found in 21 countries and territories in the Western Hemisphere. It has spread so quickly that world health officials had warned that it was only a matter of time before it reached the United States.

Francis Collins, the director of the National Institutes of Health, on Tuesday called Zika an emerging threat and urged more research into its treatment and prevention. He said a recent study found that more than 60 percent of the U.S. population — about 200 million Americans — live in areas where the virus could spread.

“In addition, another 22.7 million people live in humid, subtropical parts of the country that might support the spread of Zika virus all year-round, including southern Texas and Florida,” Collins wrote in a blog post. “Already, there are reports of local spread of the virus within Puerto Rico and of travelers returning to the U.S. with the Zika infection.”

The Aedes aegypti mosquito carrying Zika is the same one that transmits dengue and chikungunya viruses, which have caused outbreaks in Florida and other parts of the United States.

The warnings should be a wake-up call for Florida and other Southern states, which are more vulnerable because of their large mosquito populations, said Walter Tabashnick, former director of the Florida Medical Entomology Laboratory.

Since Brazil reported its first case last May, Zika has affected as many as 1.3 million Brazilians. More than 13,000 people have been infected in Colombia and roughly 500 in El Salvador, where health officials have taken the dramatic step of advising women to delay getting pregnant until 2018.

Authorities in Ecuador and Colombia have also recommended that couples avoid pregnancy.

Last week, CDC officials said pregnant women should consider postponing trips to 14 destinations, including Brazil, Colombia, El Salvador and Guatemala. On Tuesday, they added the U.S. Virgin Islands and Dominican Republic to the list.