A measles outbreak in Okinawa is causing concerns about tourism ahead of the Golden Week holidays, with 65 infections registered over a one-month period that ended Thursday, the Okinawa Prefectural Government said.

Golden Week starts later this month, but hotels in the popular resort area have already received more than 170 cancellations from Japan and overseas, it said.

The outbreak began when a Taiwanese man in his 30s was diagnosed with measles on March 20 in Okinawa.

The prefectural government is warning prospective visitors on its website to ensure they were vaccinated.

"It's hard to say 'Please come' with confidence," a government source said.

In 2015, the World Health Organization declared Japan free of measles because infections involving the indigenous virus had not been confirmed for three years, though there were imported cases of measles.

"I'm not worried because my 5-year-old eldest son has received a vaccine," a 42-year-old tourist said while strolling along bustling Kokusai-dori street in downtown Naha, Okinawa's capital.

But Satoshi Toyama, president of the Kariyushi hotel chain, was anxious.

"There may be some cancellations during the peak period," he said.

Another hotel industry source said damage was likely.

"I'm afraid the local tourism industry will be hit by rumors," the source said.

While hotels are taking preventive measures, such as encouraging employees to get vaccinated, challenges remain because the disease is highly infectious.

Measles is spread by contact with an infected person's nasal secretions or saliva. The symptoms include fever and a rash.

"As measles is airborne, there are limits to what we can do," said a senior official working in the hotel industry.