The Texas couple had been planning a trip to Fiji — relaxing on palm tree-lined beaches, perhaps swimming with manta rays or hiking in Koroyanitu National Heritage Park.

Excursions like this one had become tradition. The couple, who posted previous vacation photos on Facebook from Cabo San Lucas and Hawaii, tried to travel — just the two of them — about once a year, relatives told The Washington Post.

Late last month, David and Michelle Paul, from Fort Worth, boarded their dachshund, named Zooey, and said what they thought was a temporary goodbye to their 2-year-old son. Then the Pauls hopped a plane bound for a South Pacific adventure.

But soon after the couple arrived in Fiji on May 22, they became gravely ill. Despite medical treatment, their symptoms continued to worsen.

David’s mother, Marsha Paul, wrote in a May-27 Facebook post that the couple contracted a virus and, days later, both had died.

“David has gone on to Heaven,” she wrote. “We are so thankful the Lord has provided him eternal life thru Jesus Christ his Saviour. David is smiling in Heaven, I am sure. His and Michelle’s smiles would light up any room and I am sure you who knew him, knew that . . . Love you all. We will cry, but we are alright.”

A U.S. Department of State official confirmed the deaths of David and Michelle Paul in Fiji and offered condolences to the couple’s families.

But the circumstances surrounding their vacation and the mysterious ailment that turned their trip to tragedy remain mostly a mystery. Where did they go? What did they do?

Perhaps most important — what disease could the couple have been exposed to?

Fiji’s Ministry of Health and Medical Services told ABC News on Sunday that the investigation into the couple’s deaths could take weeks.

Not long after David and Michelle arrived in Fiji, David, 38, began messaging his mother picturesque photos from the island. On May 23, he told her the place they were staying was “very calm” and that he wished she was there, his mother told The Post.

Then on May 24, Marsha Paul said she got a worrisome message from her son. “We were at hospital all morning," he wrote. "We both caught a nasty virus. I‘ve never thrown up so much my whole life. I still feel pretty bad.”

His wife, Michelle, was texting her mother as well.

“We are both going to doctor now,” the 35-year-old wrote in messages later obtained by ABC News. “We have been throwing up for 8 hours. Dave has diarrhea. My hands are numb. We will text when we can.”

After returning from the clinic, she wrote: “They gave us fluids and anti-nausea drip. They gave us electrolyte packets and anti-nausea pills."

“We still don’t feel 100 percent,” she added, according to ABC News. “Going to rest in our room.”

David’s mother told The Post that he called her for the first time May 25, telling her that after the couple was sent back to their room, Michelle began sweating and shivering. He told his mother that he was too weak to take Michelle back to the clinic, so he called for a ride. But when they got there, he said, Michelle was laboring to breathe and, in the end, the doctors were unable to save her life.

“He sounded helpless,” Marsha Paul said of her son.

Michelle died May 25.

And just two days later, David was dead, too.

After their deaths, Fiji’s Ministry of Health and Medical Services said in a seemingly unrelated statement that it has been monitoring communicable diseases, including influenza.

Then Thursday, after announcing a couple vacationing in Fiji had become ill and died, the ministry said in a statement that influenza had been “ruled out” and that “at this stage we do not believe there is any risk to the public.” The case is under investigation, it said.

The ministry said a “small number” of health-care professionals who had come into close contact with the couple are being monitored for symptoms but are currently “well.”

The Ministry of Health and Medical Services said it is also working with the U.S. Embassy in the country, as well as the U.S. Centers for Disease Control and Prevention and World Health Organization, to help determine how the couple died. WHO said it is “providing access to laboratory and other technical services in Australia.”

Marc Calanog, Michelle’s father, told People magazine that he and his wife are caring for the couple’s 2-year-old son and that he worries about the day they will have to tell the toddler how his parents died. In the meantime, Calanog said, they are trying to hide their indescribable grief from the child.

“If we get depressed, then my grandson will be the one to suffer,” he told the magazine. “Right now, we are taking care of my grandson. We want to be strong because instead of being a grandparent, we might end up being a parent and that is a big shift from what we’ve been doing for the last few years.”

“Overall, we will recover,” he added.

David also leaves behind two other sons and a daughter from previous relationships, a relative said.

As for the couple’s dog, Tracey Calanog, Michelle’s sister-in-law, told WFAA she called numerous kennels near the couple’s home in Fort Worth and, with some help from the community, she was able to find their dog, Zooey, and take the animal home with her.

Marsha Paul, David’s mother, said family members are still searching for answers as to what happened.

“I don’t know when the tears are going to come. I carry a handkerchief with me all the time,” she told The Post, crying. “I ask the Lord each day to carry us through the day.”

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