Liz Szabo

USA TODAY

Both American athletes and sports fans have canceled plans to travel to Brazil for next week's Olympics for fear of contracting the Zika virus. Now the apparent spread of Zika to Florida, confirmed by Florida Gov. Rick Scott Friday, means that Americans could face the risk of becoming infected in their own backyards.

Scott announced that four Florida residents were likely infected with Zika, which can cause devastating birth defects, in a 1-square-mile area just north of downtown Miami. Although doctors have diagnosed 1,658 Zika cases in the continental U.S. and Hawaii, until now all the cases were related to travel and, in one case, a lab accident.

"This is a game changer," said Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine in Houston. "I’m concerned that this is just the beginning."

Pregnant women, doctors and public officials need to take Zika seriously, Hotez said. The virus could be spreading undetected in other steamy areas of the southern U.S., few of which test mosquitoes for Zika.

The Centers for Disease Control and Prevention hasn't suggested Americans alter their travel plans or that women postpone pregnancy. The agency has advised pregnant women to wear mosquito repellent, pants and long sleeves when outdoors, and to spend as much time in screened, air-conditioned buildings as they can.

Hotez said that advice may not go far enough. He said he's "concerned that we’re not giving timely and appropriate public health advice to pregnant women in at-risk areas," such as South Florida. "We may need to advice pregnant women to avoid the Miami area" during the summer months, when mosquitoes are most active.

Other public health experts worry that the arrival of Zika in the U.S. will lead to more birth defects in babies.

"This is the news we’ve been dreading," said Edward McCabe, senior vice president and chief medical officer at the March of Dimes, who said his group is "deeply concerned" that Zika appears to be spreading among home-grown mosquitoes.

"It’s only a matter of time before babies are born with microcephaly, a severe brain defect," McCabe said. "Our nation must accelerate education and prevention efforts to save babies from this terrible virus."

A variety of health groups, including the American Medical Association and the American Public Health Association, criticized Congress for leaving for summer vacation with providing emergency funding to fight Zika. Although President Obama requested $1.9 billion for Zika prevention in February, Republicans and Democrats in Congress were unable to agree on funding. Congress will reconvene after Labor Day. Both parties have blamed the other for failing to reach a compromise.

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“Public health is again being asked to do more with less to keep Americans safe," said Georges Benjamin, executive director of the American Public Health Association. "We’ll do the best we can. Damage has already been done, but when Congress comes back in September, it must make sending bi-partisan Zika legislation to the president a top priority.”

Congress should create a public health contingency fund, which could be used for a variety of emergencies, so that federal health agencies wouldn't have to wait for lawmakers to approve funding for individual crises, said Lawrence Gostin, faculty director of the O’Neill Institute for National and Global Health Law at Georgetown University.

“We have lost vital months where states and territories could have been building the capacity to control mosquitos, clean up breeding grounds and educate the public," Gostin said.