``Mama,'' his 5-year-old son, Bobby, said, tugging Stella's shirt. ``Daddy's laying on the floor.''
The illness inside Hillegass' lungs was already getting the upper hand. He'd probably gotten it from mouse droppings in a hunting cabin he had used two weeks earlier. It was too quick - and too rare - for doctors in Allentown to diagnose in time.
In death, Hillegass would become Pennsylvania's first known victim of a disease called hantavirus.
By March he would be one of two.
With two deaths confirmed in the state, the small community of scientists who study this lethal disease are turning their attention here.
They are pondering such questions as which rodents carry the virus, and where; whether other cases have gone undetected; even whether the global climate changes triggered by El Nino might help explain when and where hantavirus occurs.
The experts stress that there's no cause for panic. Hantavirus cases, as one doctor says, are less common than getting struck by lightning. At the same time, they suggest some simple steps for airing out and disinfecting any dark, closed-in space with mice around - especially in woodlands, and especially as thousands of Pennsylvanians prepare to head upstate for weekends or summer vacations.
Experts want people to know about the disease.
``It's important to get the word out there to physicians so that if they do have a case of hantavirus, they recognize it in time and don't try to treat other possible causes,'' said Joni Young, a hantavirus researcher at the U.S. Centers for Disease Control and Prevention in Atlanta. ``It helps to get the word out to the public.''
* Like AIDS and Ebola, hantavirus is known as an ``emerging infectious disease'' - one that scientists are just beginning to understand. It has killed 179 people since it was first identified in a 1993 outbreak in the Southwest.
New as it is to researchers, the virus is believed to be older than human memory. The mice who scampered around prehistoric campfires probably carried it.
``If we could study the lungs of Neanderthal cavemen,'' said Jan Humphreys, a rodent specialist at Indiana University of Pennsylvania, ``we would probably find hantavirus.''
It thrives in dark, confined spaces; air and sunlight kill it. People get it by inhaling the mist from fresh rodent feces. Researchers think Hillegass caught it from the droppings of white-footed mice, a breed common throughout the state's woodlands, even around Philadelphia.
A soon-to-be-published CDC study suggests 3 percent of white-footed mice in the Northeastern United States carry the disease.
The study says rodent research conducted at national parks in 1994 and 1995 showed a ``likelihood'' that lung-attacking strains of hantavirus would soon turn up for the first time in several states.
One was Pennsylvania.
Hantavirus is not contagious. Even so, experiments on it at the CDC are carried out in maximum-security labs, by scientists wearing bubble suits and respirators.
Suspected cases trickle in from across the country, the CDC's Young said. The research is a small part of the center's work in an era when infectious diseases such as AIDS have inflicted far wider suffering.
After Hillegass' death though, the search for other Pennsylvania hantavirus cases picked up speed.
It got a push from an Allentown disease specialist, Luther V. Rhodes 3d. He and other medical investigators, here and at the CDC, also determined that Hillegass had died of a hantavirus strain not previously seen as fatal to humans.
Rhodes was on a mission. He'd watched helplessly with other doctors and nurses as Hillegass lay dying.
``There's no greater challenge as a physician to have a patient die before your eyes,'' Rhodes said. ``I felt vacant, frustrated. Did I miss something?''
* Under a microscope, the virus that invaded Hillegass' lungs looks like peppercorns.
The tiny gray masses attach themselves to the capillaries that line the lung wall. In a healthy person, hatches on those blood vessels open and close, trading carbon dioxide for oxygen and moistening the lungs. Hantavirus somehow disables the hatches - it's as if they are stuck in the open position. Blood, along with clear blood serum, begins to pour into the lungs.
Hillegass' lungs were filling, leaving him gasping for air. Platelets in his blood rushed to his lungs; as his immune system fought back, he had a fever and aches so acute he could not stand up.
That Thursday, an ambulance took him to the emergency room in Allentown. Physicians prescribed antibiotics and sent him home.
On Friday, during Stella's night shift, a coworker came over and said her husband was calling.
``I can't breathe,'' Hillegass gasped into the phone.
``Call 911,'' she told him, and rushed home.
Hillegass was admitted to Lehigh Valley Hospital that night. Tests for known infectious diseases came back negative. By 5 a.m., nurses were inserting a tube in his throat, and a ventilator began to breathe for him.
Rhodes, an infectious-disease specialist at the hospital, was making his rounds that morning and stepped into Hillegass' room.
A bespectacled man with thinning brown hair, Rhodes, 52, had been dealing with deadly viruses since 1976, when he had treated five of the first Legionnaires' disease victims in his first year of practice in Allentown. He pondered Hillegass' symptoms: extreme pneumonia, cause unknown. Platelet count way down - signaling a struggle with a powerful foe.
``His body was sending up a red flag that it was under severe attack,'' Rhodes recalls. ``His system was going all-out.''
And the ailment didn't behave like pneumonia, which causes patients to deteriorate day by day, Rhodes said. ``He was going downhill hour by hour.''
On Hillegass' chart, Rhodes made a note: Test for hantavirus.
(The doctor credits some students with raising his awareness. Last summer, an advanced-science class at nearby Allen High had asked him to lecture on Ebola, hantavirus and other emerging diseases.)
Hillegass' blood samples were sent to the CDC and another lab.
By 8 a.m. that Sunday, Hillegass' heart was beating 170 times a minute - but the virus had so weakened the heart muscle that the beats had little strength. His blood pressure was low and dropping.
``In three days, Hillegass' heart went from the heart of a 40-year-old man to the heart of a 90-year-old man,'' Rhodes said.
Hillegass' lungs were now nearly full of fluid, a solid mass of light on his chest X-ray. The ventilator was forcing air in, but little oxygen got through - ``like pumping air into a brick,'' a doctor said later.
The patient was already on antibiotics, medicine so powerful that doctors nickname it ``gorillacillin.''
Joseph Vincent, a senior pulmonary specialist at the hospital, stood at Hillegass' bedside for more than two hours - and wrote a long note on his chart that concluded, ``The likelihood of survival is very low.''
Vincent beckoned Rhodes to watch a nurse suction the pinkish fluid from Hillegass' lungs. The six-ounce beaker filled quickly.
``I'd never seen that kind of thing,'' Rhodes said. ``The fluid just poured out of him.''
Doctors summoned Hillegass' family to his room. The heart monitor beeped slower and slower. Bloated and pale, Hillegass slipped away.
It had been fewer than 48 hours since he had checked into the hospital with what seemed like a bad flu.
In late November, Rhodes got a call from Young at the CDC.
She said Hillegass had died of hantavirus.
``My first thought was: We've missed other cases,'' Rhodes said. ``We needed to look at unexplained pulmonary deaths in people who are otherwise healthy.''
* It wasn't known at first as a lung ailment. The virus got its name during the Korean War, when U.S. Army researchers found a kidney disease among GIs stationed near the Hantaan River.
Later studies found the kidney version of hantavirus around the world, especially in port cities. In 1986, Baltimore researchers found that more than 6 percent of inner-city dialysis patients had been infected with the virus. The culprit: urban rats.
As recently as last fall, Philadelphia's top rodent-control specialist, Randall Hirschhorn, sent rat blood serum samples to the CDC to check for the kidney virus, which is rarely fatal.
Hirschhorn said the lung-attacking, or pulmonary, form of hantavirus had not surfaced in this part of the state.
``If this were around Southeast Pennsylvania, we'd know about it,'' Hirschhorn said last week. ``It's a very dramatic kind of thing that catches treating physicians' attention quickly.''
He added that the precautions suggested by the state and the CDC are wise ones: Air-out closed, rodent-infested areas and spray them with disinfectants before sweeping or vacuuming. Don't touch rodent droppings with bare hands.
Until 1993, scientists knew hantavirus only as a kidney disease. That year, in the Four Corners area of the Southwest, a more deadly hantavirus emerged.
Its emergence, some researchers would note later, came not long after El Nino's winds had brought the region a warm, wet winter, followed by an runup in the mice population.
A young Navajo couple died first. Their lungs had filled with fluid. They had lived in a trailer; researchers found it littered with mouse droppings.
The mortality rate for the new disease - called hantavirus pulmonary syndrome because it attacked the lungs - was stunning. For every 10 people infected, as many as seven or eight died.
Researchers in bubble suits combed the Navajo reservation and trapped moles, shrews and other rodents. The brown deer mouse proved to be the carrier of a strain that came to be known as Sin Nombre - without name.
By last fall, 177 cases of the lung-attacking hantavirus had been identified by the CDC, mostly in the West. It was rarest in the Northeast; one Rhode Island college student died of it after cleaning out a warehouse on Long Island. New Jersey has reported no cases.
Then, still another hantavirus - the Monongahela strain, carried by white-footed mice - proved lethal.
This strain, investigators determined, is what killed Hillegass.
The Monongahela strain had been detected in mice. Until CDC researchers spotted it in Hillegass' lungs, it had never been known to kill a human.
Rhodes notified the state Health Department and doctors in other regional medical centers, such as Hershey and Hazleton. The state Health Department issued an advisory to physicians across the state and began asking the Hillegass family where he might have been exposed to rodents.
The cabin in rural Potter County seemed the likeliest spot. Hillegass had slept in the loft. After Christmas, two state health investigators, accompanied by rodent specialist Humphreys, donned air-filtration masks and went into the cabin.
They found the loft littered with mouse droppings.
The investigators captured mice under a woodpile near the cabin and promptly dissected them that afternoon, sending lung tissue to the CDC.
Back in Allentown, Rhodes went on a hunt of his own, combing through the records of area hospitals for unexplained pneumonia deaths where the heart was weakened dramatically and the immune system was under siege in otherwise healthy people.
He found two dozen similar cases in the Lehigh Valley. But the victims were long buried or cremated. Without tissue to test, Rhodes could make no findings.
Then he remembered that the morgue at Lehigh Valley Hospital had tissue from autopsies done all over the Poconos. Surely, he reasoned, there might be another case in the plastic quart containers on the metal shelves of the morgue.
Last month, Rhodes sat down with Samuel D. Land, a bearded, 36-year-old forensic pathologist whose practice is at the same hospital, and began looking through the records of recent deaths. At first no hantavirus clues emerged.
Then Land, who had performed the Hillegass autopsy, opened the black, accordion-style file he had been keeping on his desk.
It was the file of Leeann Strunk, a Stroudsburg-area factory worker who had died of unexplained pneumonia a year earlier.
A woman who loved to garden, she and her husband lived in a trailer near the hamlet of Cresco and had two grown sons. She preferred flannel shirts and jeans; she was proud of having recently passed her high-school equivalency exam.
Strunk's death in March 1997, at age 39, had troubled Land. In his autopsy he had noted her lungs were so filled with fluid they weighed three to four times normal. He'd never been satisfied with his initial finding - that she died of an E. coli infection accompanied by ``multiple organ failure.''
Now Rhodes looked at Strunk's chart, and saw her platelet count: very low - like Robert Hillegass'.
Land sliced fragments of lung tissue he had saved from Strunk's autopsy, encased them in plastic and sent them to the CDC.
The results came back last month.
Strunk was number two.
The state's first known hantavirus victims had lived fewer than 50 miles apart.
Rhodes said, ``It cannot be ignored as a fluke when two cases are so close together.''
* At a hantavirus conference last month in Atlanta, a University of New Mexico researcher presented a paper that examined parallels between warm, wet winters caused by El Nino, and the reported cases of the virus, along with rises in rodent populations. Recent news stories in the Southwest have predicted that this year's warm winter might bring more cases.
Most experts say there's not enough evidence yet.
``If there were four or five El Nino winters followed by more cases, then we would have something to go on,'' said Humphreys, the rodent specialist. ``It's too soon to tell.''
No one knows why two hantavirus deaths struck Pennsylvania last year. Perhaps the disease has always been here and doctors have missed it.
State health officials have begun investigating Strunk's death. But the fact that she died a year ago will hinder their chances for pinpointing where she might have been exposed, state epidemiologist Andre Weltman said.
That Strunk and Hillegass lived not far apart is intriguing, Weltman said - but does not suggest any widespread infection because the disease is so rare.
``We expect it to remain rare,'' he said. ``Certainly we don't see this as any kind of problem. It would be a mistake to focus all our public health resources on this. When specific cases come up, we'll look into it as best we can.''
Weltman stressed that the state Health Department is strapped for resources in the face of more common diseases such as meningitis.
``The fact is, Pennsylvania is relatively resource-poor as it relates to public health,'' Weltman said. Given that reality, he praised Rhodes' efforts to educate doctors and find other cases.
``He's an ally to the public health,'' Weltman said. ``More power to him.''
Last month, on the day after Rhodes learned of the Strunk case, he presented information on how to identify and combat hantavirus at an infectious-disease conference in Allentown.
In the audience were doctors from around the region. Rhodes described the symptoms to watch for, and put up a slide giving the address for a University of New Mexico lab that offers quick testing for hantavirus. Several doctors in the audience wrote down the address.
Rhodes told of the few known countermeasures, such as use of heart-stimulating drugs, and a lung bypass machine that may increase patients' chances of surviving until their lungs could clear.
Another listener in Rhodes' audience was John Lapic, a Pottstown podiatrist and friend of Robert Hillegass'. Back in early November, Lapic and Hillegass had driven up to Potter County to hunt deer. They stayed in Lapic's mountain cabin - the place where experts believe Hillegass was infected.
After his friend's death, Lapic was tested for hantavirus antibodies. The results: negative.
If Hillegass caught hantavirus in the cabin loft, his friend is lucky. Lapic had spent the next day in the same loft, putting up insulation and moving items into storage.
Lapic and his wife, Judi, paid a visit last week to the Potter County cabin. Judi Lapic sprayed the interior of the cabin with disinfectant, and aired it for a while.
Those steps had been suggested in a state Health Department advisory, prepared after the CDC determined what had killed Hillegass.
As for whether other cases will turn up in the state, it's too soon to tell.
``This,'' Rhodes said, ``is Chapter One of hantavirus in Pennsylvania.''