US health officials have warned pregnant women to avoid the area of Miami Beach, Florida, after receiving confirmation that the Zika virus is active in the popular tourist destination.

The US Centers for Disease Control and Prevention (CDC) also suggested on Friday that pregnant women who are especially worried about exposure to Zika should consider avoiding all of Miami-Dade County in southern Florida.

The new warnings represent a challenge to Florida's multibillion dollar tourism industry and raise concerns over Zika's spread in the continental US.

Florida Governor Rick Scott said in a press conference on Friday that state health officials had identified five cases of Zika believed to be contracted in Miami Beach. "This means we believe we have a new area where local transmissions are occurring in Miami Beach," he said.

On August 12, the US Department of Health and Human Services declared a public health emergency in the American territory of Puerto Rico amid the rising number of Zika infections in the Caribbean island.

The US territory of about 3.5 million people has recorded nearly 11,000 cases of Zika, including 1,035 pregnant women, although the actual number of infections with the mosquito-borne virus is likely higher.

Zika was first detected last year in Brazil, where it has taken its heaviest toll so far, and has spread rapidly through Latin America and the Caribbean.

The United States reported its first locally transmitted Zika virus in Florida in July.

The virus is primarily spread by mosquitoes, but can also be transmitted by sexual contact, prompting health officials to advise that people who have been infected refrain from unprotected sex for several months.

Zika can cause microcephaly, a birth defect marked by abnormally small head size and developmental problems in babies.