The Texas couple who died suddenly from a mysterious illness in Fiji last month sent messages to relatives saying their hands went numb and that they had been throwing up for at least eight hours prior to rushing to a local doctor to be examined.

David and Michelle Paul of Fort Worth, Texas, were in their 30s and both healthy when they arrived in Fiji on May 22. According to relatives, the couple were in and out of the hospital due to a violent illness that caused vomiting, diarrhea, extreme weakness, shortness of breath and hand numbness.

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"We are both going to doctor now," Michelle Paul, 35, wrote in a WhatsApp message to parents Marc and Juliet Calanog, who live in Nevada, on May 24. "We have been throwing up for 8 hours. Dave has diarrhea. My hands are numb. We will text when we can."

"We just got back from the clinic. They gave us fluids and anti-nausea drip," Michelle Paul wrote after returning to the hotel, according to texts obtained by ABC News. "They gave us electrolyte packets and anti-nausea pills. We still don't feel 100%. Going to rest in our room."

The Fiji Healthy Ministry ruled out “influenza” and is continuing to work with the U.S. Centers for Disease Control and Prevention and the World Health Organization to determine what sickness killed the couple. "It would be premature to speculate further on the cause of death until the investigation is complete," the agency said in a statement Tuesday.

Michelle Paul returned to the hospital where she died on May 27. Her 37-year-old husband died two days later. David Paul’s sister, Rebecca Ward, revealed that her brother wrote to their mother on Facebook as his wife’s illness worsened.

“When my brother woke up, Michelle was just clammy and sweating and he was too weak to take her to the hospital himself," Ward said on Good Morning America on Wednesday. "They couldn't get her an IV, couldn't revive her, and that's when she passed away."

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"Not long after that, my brother ended up at the hotel, then later on that day he went back to the hospital. He got released again and we thought he would be able to come home," she said. "Then the next thing we hear he was back in the hospital with shortness of breath and that was the last time we actually talked to him."