"Three hours later she passed away," Zermeno said. Staring at a picture of his mother, he added, "She had a great attitude about life."
But, as CBS News Correspondent Vince Gonzalesreports, the end of her life was just the beginning of the Zermeno family's ordeal. Zermeno called his wife Patty. She, and his daughter Zola, now 8-years-old, began the long drive to Texas.
At a teacher's urging, Zola began a journal. In one of the first entries she wrote: "Hearts are broken in Texas. We are not to the sadness yet. We are only on the road."
They arrived in time for the funeral.
The morning after the funeral, Zermeno's sister Eva woke up with a 104-degree temperature.
"We immediately called 911 to get her to the hospital," says Zermeno. "She was talking to us as we loaded her into the ambulance: 'Don't worry. Everything's going to be OK."'
At the hospital, doctors said Eva had pneumonia and a kidney or urinary tract infection, but said she would be fine. The next day Eva was dead.
"We were in disbelief," said Zermeno.
"So now we're planning funeral number two," said Patty. "Within 24 hours of mom's funeral, Eva's gone."
The official cause in both deaths was deemed septic shock, a catch-all finding that usually means the real cause is unknown.
But the family wanted answers.
"We started to talk about the similarities between mom's death and Eva's death," Patty said.
Even Zola noticed and wrote in her journal, "Eva died almost the same way my grandma did."
The family - not the doctors, nor the coroner - began to suspect hantavirus, a deadly disease carried by deer mice that causes flu-like symptoms. It was first identified during a 1993 outbreak in New Mexico. Cases and new strains of the virus have now been reported in 31 states.
"I called the hospital and asked if that was one of the considerations or diagnosis that they had thought about," Zermeno said. "They had not."
The family asked the coroner to test Eva's blood for hantavirus. It was positive, and now grief turned to fear. They cried and held each other because they knew the virus could be caught by inhaling dust containing fragments of mouse droppings, which Zermeno found while cleaning the house Eva and her mother shared.
"When we were in the pantry and I opened up (a) cabinet that hadn't been opened for a long time and stirred up dust, that's exactly when I was exposed," Zermeno said.
And just a few weeks later he got sick. His wife rushed him to the hospital and explained he'd been exposed to hantavirus.
"The people at the hospital looked at us like we were nuts," Patty said. "They had no clue."
"They didn't know what they were dealing with," said Zermeno. "We knew more than they did."
Then an infectious disease specialist told him not to worry and sent him home because the hospital did not detect the virus in his blood.
"He sat down and told us, 'I am 99.9 percent sure that you do not have the hantavirus,'" Zermeno said.
He was wrong, and the next day Gilbert was back at the hospital with a 104-degree fever.
"When the second infectious disease doctor came in and confirmed it was the hantavirus, that's when I had my conversation with God," said Zermeno. "And that's when I said, 'You know, I'm OK with whatever you decide. I'm OK if you decide to take me because I've got my mom and sister up there.'"
It's a miracle Gilbert survived because nearly half of all hantavirus patients die. In fact, a review of hantavirus deaths by CBS News found, in case after case, that hospitals across the country misdiagnosed the virus and sent the patients home. Many later returned but it was too late.
And it happens even in areas where doctors and nurses should know better. Hardy Haceesa, a member of the Navajo Nation, developed a fever after cleaning out an old shed. His wife took him to government hospital not far from where the original hantavirus outbreak took place.
The family's lawyer, James Lyle, said, "He goes into the hospital. He tells the person staffing the emergency room, 'I think I might have hantavirus,'" said James Lyle, the family's lawyer. "The person staffing the emergency room, in the geographic center of the world for known hantavirus cases, doesn't know what he's talking about."
Haceesa was told he had bronchitis and sent home. Another hospital also missed the disease and he died.
"I think it's very easy to believe that there are many people who have died from hantavirus that we'll never know about," Lyle said. "We may just be scratching the surface in terms of how many people really are dying from the disease."
In fact, since 1993, the government says 123 people have died from the virus. But the actual number may be much higher. One federal health official told CBS News it may kill more than 100 people a year, but those cases aren't reported because doctors often miss the disease.
"And the true number is anybody's guess," said Dr. Brian Hjelle, one of the nation's top hantavirus researchers. The University of New Mexico scientist agrees cases are being missed. "It wouldn't surprise me to find that there were a hundred fatal cases a year that were missing."
Hjelle says there are gaping holes in the government's surveillance system and the Zermeno cases are the perfect examples.
"Case cluster with hantavirus are very unusual so you can extrapolate from that there are probably quite a lot of individual cases where someone dies and they're not diagnosed," said Hjelle.
The hantavirus is so deadly that even at outdoor testing labs in New Mexico scientists working with infected mice must wear protective suits and respirator systems. In fact, the government classifies the hantavirus as a potential biological weapon.
"Because it's transmitted through the aerosol route, because there's no treatment or vaccine, because it has such a high-case fatality ratio," said Hjelle. "I think that was a wise decision to categorize it as a category agent of potential bio-terror."
He and his team developed a vaccine that works on mice, but there's no funding for a vaccine to protect humans. And Hjelle believes the holes in hantavirus surveillance could cause more than just bad statistics.
"We don't know how many people get it," said Hjelle, "And we would have a harder time, because of that, picking up an intentional release of the agent."
Now recovered from hantavirus, Zermeno who has covered tragic stories at CBS Phoenix station KPHO, hopes his own family's tragedy will help focus attention on this deadly disease.
"It wouldn't surprise me that there are a lot of people out there that have passed away because of this virus and they didn't know what killed them," he said.