June 19, 2006
Student Scene
Hantavirus: Bountiful Season Brings Deadly Harvest
 Photo
by Graham Ramsay
Ellen Rothman |
Mr. Hathale lay in the first bed of the emergency department. By the time I arrived for my morning shift, he had been there for several hours. He was in good spirits, telling jokes. Without his dentures, he had difficulty enunciating, and the oxygen mask over his mouth further muffled the words. Mr. Hathale was waiting for a medical transport team to fly him from our remote town on the Navajo Reservation to the intensive care unit at the University of New Mexico Hospital, more than 300 miles away.
I reviewed the case. Could Mr. Hathale really have hantavirus? On the one hand, he seemed too healthy, and he had no fever, a hallmark of the disease. Yet the number of platelets in his blood was profoundly low, the most ominous sign of a disease that has no rapid diagnostic test. I also noticed that he was breathing rapidly, and his X-ray revealed inflammation in his lungs. These were all worrisome findings, so we decided to transfer him to the national center of excellence for this rare disease.
Hantavirus has no easy diagnosis, no cure, and it kills more than a third of its victims. It is exceedingly rare and resembles other viral illnesses during its early stages. The only available treatment is supportive care, including heart/lung bypass machines, to allow time for the pronounced inflammation in the lungs and heart to subside. Even the young and healthy die.
A Killer’s
Profile
While there have been scattered cases of hantavirus throughout the United
States, it is endemic to the Four Corners region. It first came to light
when a cluster
of cases was identified on the Navajo Reservation in 1993. A previously
healthy young Navajo woman, who was initially diagnosed with a flulike
viral infection,
developed progressive respiratory failure and died. Within a week, her
19-year-old fiancé also died. That summer, more than 50 other
similar cases were identified.
|
“Examinations revealed that hantavirus had been endemic to the area for decades, corroborating the Navajo lore.” |
Investigators from the Centers for Disease Control and Prevention uncovered a previously unknown strain of hantavirus as the culprit. Navajo medicine men had long noticed outbreaks of a fatal illness after wet summers, when exceptionally large crops of piñon nuts led to an increase in the mouse population. This observation matched existing knowledge about other strains of hantavirus and led researches to identify deer mice as the vector. The investigators also examined stored autopsy specimens from individuals who had died of undiagnosed respiratory failure in years past. These examinations revealed that hantavirus had been endemic to the area for decades, corroborating the Navajo lore.
Hantavirus is concentrated in mouse urine. Most patients become exposed when cleaning out mouse-infested areas, such as sheds. After a two-week incubation period, the virus causes a flulike illness characterized by fever and muscle aches. Several days later, patients develop rapidly progressive inflammation that leads to respiratory and cardiac failure.
Lethal Bloom
Last year, we had an unusually wet spring. By May, normally bare red
rocks were awash in cacti with lurid yellow and magenta flowers. The
yucca bloomed
in bell-shaped white flowers standing tall above a desiccated fan of
spiny leaves. Arid valleys transformed into golden vistas of flowers
gently swaying
in the breeze. In my four years on the rez, I had never seen the desert
bloom before. The spring of 2005 was reported to be the wettest season
on record
in our area since 1993. That summer, when we drove over dark roads,
our headlights startled mice dashing across the asphalt.
We settled into an uneasy season. We feared an epidemic, but no one in our area turned up positive for hantavirus. Indeed, only a few cases of the infection were reported across the reservation. As the days turned cooler, we lowered our guard. We had made it through yet another summer.
Our first case of hanta took us completely by surprise. A teenager we had seen over the Christmas weekend in 2005 collapsed and died in a nearby hospital shortly before the New Year. That weekend had been the peak of an influenza outbreak, and we saw many patients with fevers and body aches. There was nothing to set this child apart. Plus, hanta is not supposed to be a wintertime disease. She had been hospitalized for more than a day before suspicion was raised for hantavirus. By the time she was transferred to a university hospital, her respiratory failure was advanced. She died on the heart/lung bypass, and hantavirus was confirmed postmortem.
We admitted Mr. Hathale to the hospital this spring. Although I had been uncertain about his diagnosis the morning we sent him, he was already on heart/lung bypass by late that afternoon. Two days later, blood tests confirmed the diagnosis of hanta. He was on bypass for a full week and ultimately recovered from the illness.
The desert landscape is subtle, and the unsuspecting eye sees nothing but a barren expanse. Last year after the spring rains, I glimpsed the desert’s concealed bounty; this year, its veiled danger.
The names used in this column are pseudonyms, and the opinions expressed are not necessarily those of Harvard Medical School, its affiliated institutions, or Harvard University.
Copyright 2006 by the President and Fellows of Harvard College