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Fall 2013

Robert Baker - 1993 hantavirus epidemic

by John Davis

Anatomy of an Outbreak

How scientists in public health, medicine, science and Texas Tech tissue libraries worked together to understand the 1993 hantavirus epidemic.

Texas Tech Research Played Key Role in 1993 Hantavirus Epidemic

In 1993, the Four Corners region of the southwestern United States was the site of an outbreak of the hantavirus. The Natural Science Research Laboratory was contacted to use specimens from the frozen tissue collection to help in the research of this outbreak.

On Friday, May 14, 1993, a young Native American from near the Four Corners region of New Mexico had just been admitted into the emergency room at Gallup Indian Medical Center. His chest X-rays showed a white-out in his lungs, which had filled with fluid.

Dr. Bruce Tempest, chief of medicine at the hospital and a commissioned officer with the U.S. Public Health Service (Indian Health Service), studied the film and tried to ascertain why this strong, otherwise healthy individual lay in shock so close to death. Little did he know that as he looked for answers, he’d find himself at the beginning of a mysterious epidemic soon to become a household name around the world: hantavirus.

As headlines blared fears of a new disease that might even be an escaped bio-weapon, scientists at universities and public health organizations raced the clock to learn more about the virus and from where it came. Robert Baker, a Horn Professor of Biology at Texas Tech University, had a feeling some answers may lie in the tissue library of the Natural Science Research Laboratory (NSRL) at the Museum of Texas Tech University.

That was 20 years ago, before myriad pieces of an intricate puzzle gave us a clear view of how the disease suddenly leaped onto the scene. Tissue samples from Texas Tech showed the virus was not new to the area. The Four Corners region adapted to the “new” threat that really was there all along. And people like Robert Bradley, a professor of biology and curator of mammalogy at the NSRL, use the skills, knowledge and technological advancements that came during and after hantavirus to see what else might be brewing in our own backyards.

On the Front Lines

Robert Baker

Transmission electron micrograph of the Sin Nombre hantavirus, first recognized in 1993.

It still hurts some people in the Four Corners area to think about the hantavirus, Tempest said. A group of young, healthy people died. Families lost members. Because the virus attacked more Native Americans, racial issues swirled, and people were stigmatized and labeled.

“It’s not a good memory for people living around here,” he said. “But scientifically and medically, there was a lot that happened, and a lot of new things were found. It’s got its good and bad points. One thing I tell my friends is that this whole thing was worked out with tax-supported institutions; the federal government, the Indian Health Service and the state government. It was all tax money at work. And the people who were here worked very hard. Nobody said ‘I’m worried about catching this thing.’ When I looked back on it, nobody really thought they were going to get sick from being involved, which has happened with other diseases with people refusing to care for sick people. There was none of that.”

Tempest wondered if plague might be a factor in the dead patient’s sudden demise. That disease occurs in animals living in the area, though rarely involves humans. However, a pneumonic plague victim could portend a major health problem for the community, he said.

The tests for plague came back negative.

“That same day, I found out that his fiancé’s family was actually having a funeral for her across the street from the hospital,” he said. “I was told she had died a couple days before. So here are these two young, healthy and athletic people who had died, who obviously were living in the same environment.”

The man’s fiancé had died at another hospital about 60 miles away, Tempest said, and he had remembered speaking to the chief of medicine there about the strange case that had stumped doctors at the other hospital, too. The woman had come into the hospital with the same sort of symptoms: severe muscle pain, fever for several days, and then rapidly developed respiratory failure, shock and died.

“When he called me, this young woman was still alive,” he said. “We talked about what it could be, but we weren’t able to come up with a diagnosis. In trying to think what was going on, it didn’t fit anything I could think of off the top of my head.”

Tempest talked to other colleagues and discovered that a patient had come into the hospital with the same group of symptoms six weeks before during the Easter weekend. Then he remembered a chart he’d been given for review of a patient who died with the same mysterious symptoms six months before at another Indian Health Service hospital 100 miles away.

Piece by piece, Tempest could see that a new or emerging health threat might be taking hold in his community.

“By end of the day, I had put together five patients who were young and healthy and had this very strange syndrome,” he said. “I called the physician at the state health department who was in charge of infectious diseases, who talked to some of his colleagues, and they didn’t have any likely answers. In the meantime, we got the medical examiner to take jurisdiction, and we also had collected the laboratory stuff that we would be running over the next day or so. We planned to talk again on Monday.

“Well, on Monday, we didn’t have an answer from the medical examiner, and all tests we had done were negative. That’s when we really started working on it by getting more people at the health department involved and starting an investigation. Eventually we ended up calling in the Centers for Disease Control and Prevention (CDC) as well. It moved rather quickly once we recognized there were at least five patients spread over a couple months. We really started getting concerned.”

Robert Baker

Robert Baker is a Horn Professor in the Department of Biological Sciences in the College of Arts and Sciences, and director and curator of mammals and genetic resources at the Museum of TTU's NSRL.

Library of Life

In Lubbock, Baker remembers reading a story on the front page of the Lubbock Avalanche-Journal that said the disease might be an escaped biological weapon. Tempest remembered rumors that a biological agent may have come from an army ammunition depot outside of Gallup, N.M.

While that might have been a possibility at the time, Baker thought the likely culprit was a disease already in the environment that just hadn’t had the opportunity, or the right conditions, to find its way into the human population.

Health officials trapped rodents around victims’ homes trying to find which species carried the virus. Soon they had their culprit–the deer mouse.

“At the time I got involved, I think scientists already thought it was probably a zoonotic disease carried in some other organism,” Baker said. “I knew we had the stuff in the NSRL that would answer the question of how widely ranging the disease might be. I called the CDC and said, ‘We can answer the question because clearly this is going to be something coming out of a reservoir species.’ When they had identified the mouse that harbored it–the deer mouse–I told them we had stuff in our museum that was 15 years old from over much of the U.S. And molecular methods would allow researchers at the CDC to identify if it was something that was recombinant DNA, (meaning a virus that had blended to make another virus that was more virulent), or if it was a naturally occurring disease.”

Scientists had been cataloging for decades biological samples and their geographic locations of origin in the NSRL’s database, originally one of three other repositories like it in the country. The building preserves a library of natural specimens for education and research purposes to record the biodiversity on the planet as well as a historical reference for documenting changes in the environment and the effects of the change on wildlife and humans.

The mammal collection at Texas Tech ranks fifth among academic-affiliated collections and eighth in size of all mammal collections. It houses species from all continents and 107 countries, with an emphasis on species from the southwestern U.S., and Central and South America. Specimens collected from Chernobyl also are housed here, Baker said, and have been used to show that even in the most radioactive areas, the gross mutations that most scientists expected aren’t occurring.


“One thing Texas Tech has specialized in is building up a huge genomic resources collection,” Bradley said. “We were one of four major universities, which included Berkeley, University of New Mexico and Louisiana State University, that started collecting this in early to mid-’70s. We have 300,000 vials of tissue from all over the world. People can use them to look for viruses.”

Originally conceived as a resource for identifying species through morphology and genetics, Baker said the hantavirus epidemic showed that the specimens could also be used to detect viral material trapped in the frozen tissue.

By looking at lung tissues from deer mice tissue samples from the NSRL, Baker determined that the disease was from the area, had been there years before the outbreak occurred and that bioterrorism or a recombinant form of another virus were not at play.

Baker and Tempest both explained how El Niño weather events before had caused greater rainfall, providing more food for the deer mice. That, in turn, drove a population explosion and created more animals carrying around more of the virus, which Tempest said he suddenly noticed almost each morning when he would find dead deer mice in his bathtub brought in by his housecat.

Victims of the disease often were living in rural areas, Baker said, in buildings where mice were able to complete their life cycle, and their urine and feces were able to accumulate. Mice weren’t affected by the virus, but carried it with them. While not a robust virus and easily killed with cleaning supplies and even by the sun, the virus would infect the human host when they breathed in aerosolized particles of the mouse waste.

“We had all the epidemiology we needed to know about how the disease was spreading in three weeks,” Tempest said. “We made videos, all kinds of posters and handouts for public education. It was fortunate we got an answer in three weeks. I think things would have started spiraling down. Just being able to put a name on something makes a huge difference.”

Taking Heed of the Warning

Since the initial outbreak and the public health education that followed, people living in the Southwest have learned to be careful around rodent droppings. That’s not to say that cases don’t still occur, but Tempest said people, by and large, have adapted to keep their properties as rodent-free as possible while using caution when getting around rodent droppings.

CDC Map - hantavirus cases, by state of exposure

CDC map of hantavirus cases, by state of exposure as of Feb. 28, 2013. Click to enlarge.

According to the CDC, 53 people were reported to have contracted hantavirus through Dec. 31, 1993. Males comprised 57 percent, and the median age of sufferers was 31. Of those diagnosed, 26 were American Indians; 22, non-Hispanic whites; four, Hispanic; and one, non-Hispanic black. Death occurred in 60 percent of the cases.

The CDC reported 556 cases occurring from 1993 through the end of 2011. Of the people ill with the disease, 63 percent were male, but now 78 percent of the cases affect whites and only 18 percent of the cases involve Native Americans. Hispanic cases have increased to 20 percent while blacks have remained the same, and Asians accounted for 1 percent of cases. (The CDC considers Hispanic ethnicity separate from race, thus the higher percentage total.) Death has occurred in 36 percent of cases.

The organization also has identified 31 cases retrospectively by examining samples of tissue belonging to people who had died of unexplained adult respiratory distress syndrome. The earliest case found so far is a 38-year-old Utah man who died in 1959.

Baker said scientists found a relation to the disease in the Four Corners region with a similar virus discovered in the 1950s during the Korean War. Called the Hantaan virus after the Hantaan river flowing through South Korea, scientists used the old virus’s name as the moniker for the new because of its relation.

“At the time the Four Corners disease was discovered, it was a new disease, and they knew very little about how wide-ranging it was,” he said. “Today we understand that hantavirus is distributed over much of the world. The hantavirus in Scandinavian countries makes everyone get a runny nose, but it’s not a really life-threatening disease. It’s in lots of different creatures. It’s been described in shrews and bats, and each one of these is unique. And some of them do get into human beings, but most of them don’t. We understand a lot more about reservoir species today–the ones that have the virus. That interaction is very significant.”

Scientists have even sequenced the genome of the differences in the virus so they can tell from which part of the country a viral strain originates, Baker said. Recently, doctors pinpointed Tucson, Arizona, as the origin in a patient in Lubbock who recently succumbed to the virus.

Robert Baker

Robert Bradley is a professor and associate chair in the Department of Biological Sciences in the College of Arts and Sciences.

The 1993 outbreak piqued the curiosity of scientists at health organizations such as the National Institutes of Health (NIH) and CDC, Baker said, to find out what other diseases might be waiting for the right circumstances to crop up in the human population.

And that’s what people are doing, Bradley said. With more than 300,000 vials of tissue from all over the world, researchers can use them to look for, say, better anticoagulant enzymes in vampire bats to create better medicines for heart attack victims, as well as rogue viruses.

“It changed the way people think,” Baker said. “We, the public, felt like we knew every disease out here. Now we know there are 20 other diseases killing people, not very frequently, and we know they exist, but we don’t know what they are or what species of rodents are carrying them. There’s a lot of work to be done to answer those questions.”

Baker said epidemics can occur right under people’s noses. While working in the Kyrgyz Republic several years ago, he and other researchers found a tick-borne encephalitis that had not been discovered before.

“It was in a national park at the northern end of the Himalayas,” Baker said. “Really, a great place to hike and work. We asked our colleagues to go to the hospital and ask if they were finding people bitten by a tick who were sick. Our colleagues asked people at the local hospital, and they said, ‘Yeah, there’s a guy in here today bitten by a tick, and he’s really sick.’ Our team was able to get blood samples for him, and they proved to be positive for this new tick-borne encephalitis. He died about two weeks after that. We knew there was a huge outbreak of virus in this guy. They had no idea this virus was present there. We need to do a lot more work and find out where viruses are and where they’re carried.”

“I think the hantavirus research was the tip of the iceberg.”
– Robert Bradley

That’s what Bradley and viral expert Charles Fulhorst at the University of Texas Medical Branch at Galveston are doing currently.

He agreed that more research is needed to know what diseases may lay waiting for the right circumstances.

“I think the hantavirus research was the tip of the iceberg,” Bradley said. “We had a lot of virologists and field biologists together, and they questioned if this hantavirus is in our backyard, what else may be out there. The ’90s were a time of a lot of survey work.”

In South America, arenaviruses are virulent, often targeting the victim’s kidneys and sometimes the brain and lungs. Fatalities are high, and woodrats are known to carry the disease.

But in North America, the disease is not virulent and seldom fatal, he said. He and Fulhorst are looking in the samples of the NSRL to see what North American arenaviruses might be lurking in the tissues that might be useful in treating the more deadly strains, or might be deadly and currently unknown. Bradley and Fulhorst are using some of the same techniques and later technologies that came from the hantavirus outbreak to keep an eye on arenaviruses.

“It turns out we had a lot of samples sitting around in the freezer that contained a lot of new viruses,” he said. “We started a screening process in different states to see what we could turn up. We found them in specimens from Texas, New Mexico and throughout Mexico and turned up a few in Arizona. Right now, we’re describing a new arenavirus from the Dickens area. It was here, and we didn’t even know about it until we started looking for it.

“I think one of the major focuses of CDC and NIH is to support research and general survey work, so we can see what’s out in natural environment, so we do have a history of these diseases, and we do know if it’s something new or been out there 30, 40 or 50 years. Viruses are always evolving as fast as they can, so staying on top of them is a very important thing to do.”

Knowing what’s out there and where it comes from may become even more important as human encroachment into rainforests and rural areas not typically inhabited by people may unintentionally put them in harm’s way. Hollywood has made several movies featuring an outbreak of a deadly virus, Bradley said. But the possibilities portrayed on the screen aren’t far from what might actually occur.

“As rainforests are being cut down and towns and communities are expanding, people are coming into contact with rodents they haven’t been in contact with in previous history,” he said. “Think of all the commerce and people moving around. People on airplanes. People fly from Asia to Europe and North America and within days, the flu arrives in our backyard. In a matter of days you could have a disease spread worldwide. The CDC worries about that.”

About the Natural Science Research Laboratory

TTU Natural Science research Laboratory

The Natural Science Research Laboratory (NSRL) is a division of the Museum of Texas Tech University that archives biological samples and their associated data in a geographically defined database. The NSRL is committed to building and preserving a library of our natural heritage for education and research purposes. The NSRL serves as a foundation for understanding and biodiversity and appreciation of life, in all its forms, on the earth, as well as a historical reference for documenting changes in our environment and the effects of that change on wildlife and humans. The causes and/or effects of animal-borne diseases, environmental pollutants, parasites, climate change, habitat loss, geographic isolation, and natural evolutionary processes and speciation are just a few examples of the investigations that can be conducted utilizing specimens and tissues archived in a natural history collection.

The NSRL houses four major collections: the Recent Mammal Collection, the Ornithology Collection, the Invertebrates Collection, and the Genetic Resources Collection.

In the U.S., the NSRL Mammal Collection ranks fifth among academic-affiliated collections and eighth in size of all mammal collections. The addition of 34,000 specimens from a recently acquired collection should move the NSRL to second and fifth, respectively. The Mammal Collection is available on the NSRL website and is searchable by species, locality and catalog number.

NSRL Research

Another way the NSRL aids the public is through its cutting-edge research that has made advancements in science, health, and safety. Some projects include:


John Davis is a Senior Writer in the Office of Communications & Marketing at Texas Tech University.

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Nov 24, 2015