How borders are drawn and enforced has far-reaching consequences, whether we live on either side of them or halfway across the world.

The British government is urging pregnant women traveling to Florida to postpone their trips after the popular tourism destination confirmed the United States’ first locally transmitted cases of the Zika virus. Women who are traveling to Florida should also avoid getting pregnant while on the trip or for eight weeks after returning, Public Health England said.

Fifty-three cases of Zika have been reported in the UK, according to The Guardian.

On Friday (July 29), Florida’s Department of Health said that the cases are concentrated in the Miami area and were likely transmitted by mosquitos. Zika has been mostly spread through infected mosquitos, but the Florida state government said no mosquitos have yet tested positive for the disease, which can cause severe fetal brain defects, such as microcephaly.

Canada’s government also warned travelers about Zika in Florida and reiterated its guidance to “avoid travel” to countries with mosquito-borne Zika.

Travelers are already shown to be more cautious this year, especially when it comes to international trips. Concerns about Zika and terrorism have prompted some tourists to pay for more expensive travel insurance that allows them to cancel their plans for any reason.

The Zika threat could be a blow to Florida’s $89 billion tourism industry, which was already grappling with a decline in foreign tourists. The state logged 2.28 million visitors from abroad in the first quarter of the year, down 6.3% from a year earlier, according to the tourism board.

Winter is a high-demand season for Florida, whose beaches draw millions escaping cold northern winters. If the disease continues to spread, it could catch Florida right when its hotels and airlines are relying on chilly tourists the most.

An earlier version of this story included an outdated figure for the size of Florida’s tourism industry.