Two U.S.-based cruise lines are forbidding people with Chinese, Hong Kong or Macau passports from boarding their cruise ships, according to company statements released Friday.

Norwegian Cruise Lines and Royal Caribbean International released statements as the coronavirus continues to spread. The companies say the new policies apply to anyone -- guest or crew member -- with these passports, regardless of residency or where they visited last.

The policies also prohibit boarding from travellers or crew members who visited Hong Kong or Macau within the last 15 to 30 days.

Norwegian Cruise Lines said passengers denied boarding will be issued a refund if they provide proof of travel.

"The safety, security and well-being of our guests and crew is our number one priority," Norwegian Cruise Lines said in a statement.

Royal Caribbean said anyone who was on a ship with a modified itinerary would receive a two-day refund in the form of an onboard credit, along with other perks.

"We take this very seriously and have a responsibility to maintain a safe and healthy environment on board our ships, as well as in the ports we visit," Royal Caribbean said in a statement.

The coronavirus emerged from China two months ago. It has killed 724 people, mostly in China, and paralyzed the world's second biggest economy. It has infected more than 31,000 in more than 25 countries and territories. The U.S. has at least 12 confirmed cases, with hundreds more evacuees from China due back Friday.

As the new policies were implemented, four passengers from a Royal Caribbean cruise ship that docked Friday morning near New York were taken to the hospital for evaluation for coronavirus.

None of the four passengers taken to a hospital showed "any clinical signs or symptoms of coronavirus" on board, Royal Caribbean said in a statement. One tested positive for the flu. They had not been in China since January 26.