(CNN) A couple from Japan tested positive for novel coronavirus shortly after visiting Hawaii this month, and Delta Airlines says it is notifying passengers who were on their flight home about the couple's diagnosis.
Hawaiian officials, meanwhile, say they've been looking into the couple's activities in Hawaii, and are trying to find people who may have been in close contact with the couple.
The man and woman were on Maui from January 28 to February 3, and then on Oahu from February 3 until their Delta flight home on February 6 to Nagoya, Japan, Hawaiian health officials say.
"We are proactively reaching out to customers who were onboard that flight as well as taking the necessary steps to ensure the safety of our customers and crew," Delta said Monday.
That roughly 10-hour flight, Delta Flight 611, departed Honolulu on the afternoon of February 6 and, after crossing over the International Date Line, landed in Nagoya on the evening of February 7.
Hawaiian state health officials announced on Friday -- eight days after the couple left Hawaii -- that the man had tested positive for coronavirus in Japan, and was being treated at a hospital there.
Those health officials said that the US Centers for Disease Control and Prevention had informed them Friday of the man's diagnosis.
Over the weekend, The Japan Times reported that the wife, too, was diagnosed with coronavirus.
In a news conference Friday, Hawaiian state health officials said this about the couple's time in Hawaii:
• The man had no symptoms on Maui, which they visited January 28 to February 3.
• The man did have cold-like symptoms, but no fever, on Oahu, where they were staying February 3-6.
• While traveling in Oahu, the couple stayed at a timeshare at the Grand Waikikian by Hilton Grand Vacations in Honolulu.
• The man wore a mask during his flight back to Japan, and may have worn a mask during other parts of his travel.
• The man did not seek medical care until arriving back in Japan, where he'd developed severe symptoms, state epidemiologist Dr. Sarah Park said.
• "It's very likely the (man) was exposed in Japan (before he traveled to Hawaii) or in transit coming to Hawaii, and became sick when he was here," Hawaii Director of Health Bruce Anderson said.
Details about when and where his wife developed symptoms weren't immediately available.
Park said that because people can get sick up to 14 days after exposure to coronavirus, she has alerted physicians in Hawaii "that it's possible that cases may surface sometime before" this Friday, two weeks after the couple left Honolulu.
"Our focus really is about his whereabouts while he was on Oahu, because that's when he developed symptoms," Park said.
CNN's attempts to reach the Grand Waikikian for comment weren't immediately successful.
The state Department of Health looked into the couple's activities in Oahu and located a man they spent time with there, Lt. Gov. Josh Green told CNN affiliate KHON.
That man "is in two weeks of home isolation now," Green told KHON.
The novel coronavirus has spread throughout the world since the first cases were detected in central China in December. At least 1,800 people have died and more than 73,000 people have been infected. At least 980 of those cases have been outside mainland China.
China's National Health Commission has confirmed the virus can be transmitted from person to person through "droplet transmission" -- where a virus is passed on due to an infected person sneezing or coughing -- as well as by direct contact.
This is not the first time officials have contacted passengers of a US-connected flight that had a symptomatic coronavirus patient.
Two sick passengers traveled from China to Los Angeles -- one on January 20, and the other on January 22, the CDC has said.
Health authorities contacted people who sat in the same rows as the sick passengers, as well as those in the two rows in front and behind.
Those passengers were told to watch for symptoms, including fever, coughing and trouble breathing. But none of those passengers became ill, the CDC said.
Correction: An earlier version of this story had an incorrect name for Hawaii Director of Health Bruce Anderson.