The spread of the Zika virus moved beyond the Miami hotzone where the first homegrown cases in the U.S. emerged, with federal health officials issuing a travel advisory Friday recommending pregnant women avoid traveling to Miami-Dade County.

The advisory also warns that expectant mothers, in particular, avoid a part of Miami Beach where five "homegrown" cases of the virus were confirmed.

The Centers of Disease Control and Prevention advisory came as the 1.5-square-mile area of Miami Beach was designated as the second zone in the U.S. where transmission of the homegrown Zika virus is now actively spreading.

The first is the Wynwood arts district in Miami, where Zika transmission was identified three weeks ago. The mosquito population there is still said to be active, but shrinking, officials say. 

In issuing the travel advisory, Tom Friedan, the head of the CDC, said Friday that the virus is not necessarily spreading throughout the entire county, but there have been instances of mosquitoes infecting individuals in Miami Beach and Wynwood.

Zika is linked to birth defects in unborn children of women infected with the virus, including a condition known as microcephaly that causes babies to be born with abnormally small heads. The mosquito-borne virus is also linked to a smaller number of cases involving neurological problems in adults.

In Miami Beach, the Zika transmission zone is a small area that stretches from 8th Street to 28th street, and runs the length of the city from the beach to Biscayne Bay. This area encompasses the city’s Art Deco district, which plays a key role in greater Miami’s $24.4 billion tourist industry.

At a Miami Beach press conference late Friday, Mayor Philip Levine tried to quell worries about the impact on the hospitality industry, with some hotel cancellations said to be already occurring, by noting that the CDC had issued “an advisory” and not a travel ban.

But he also attempted to underscore the city’s commitment to safeguard the health of tourists and residents.

“I don’t want to minimize this concern in any shape or form. This is something that we all take very seriously and our city is taking very seriously.  For pregnant women, the CDC advises extraordinary measures and they all ought to do that,” said Levine.

“Forty-seven states in the U.S. now have Zika. It’s not just Miami Beach, but anything that happens in Miami Beach reverberates around the world. I learned that a long time ago.”

City officials have been working with Miami-Dade County authorities for weeks to eradicate Zika-carrying mosquitos and these efforts will now be redoubled, Levine said.

But aerial pesticide spraying, which has been underway in Wynwood, and is credited with helping shrink the mosquito population there, is not considered appropriate for Miami Beach at this time, partly out of concern for the ocean, a Miami-Dade county official said.

There have been 2,260 cases of Zika reported in the U.S. as of Wednesday, according to the CDC, mostly acquired through travel to other countries where the virus has been circulating. 

As of Friday, the Florida Department of Health counted 36 individuals in Florida who've become infected through local transmission and 488 individuals whose infections stemmed from traveling outside the country to an area of mosquito-borne transmission or from having sex with such a traveler.

Of all the individuals with Zika, 68 are pregnant women.