Turkey’s health minister, Fahrettin Koca, issued a statement saying that the 15 people infected with the variant were in isolation and that their contacts were being traced and placed under quarantine. In countrywide checks, the statement said, the virus had not been detected in anyone other than travelers who arrived from Britain.

The finding brings the number of countries that have detected the variant to at least 33 since Britain announced finding it on Dec. 8, and the number of countries barring travelers arriving from Britain to more than 40. Some countries are also imposing restrictions on travelers, including U.S. citizens, who in recent weeks visited the countries where the variant has been detected.

The Philippines expanded restrictions on travelers from Britain and 18 other countries, adding the United States after a third state, Florida, reported an infection involving the variant. Many countries have already restricted travel from the United States because of its staggering number of infections — the most in the world.