Hantavirus: Ecology and Disease in US, Chile, and Panama

OverviewPathogens and Museum CollectionsMSB and HantavirusesSin Nombre
Hantavirus (SNV)		SNV and Traditional Ecological KnowledgeFurther
Learning

 

The initial outbreak and subsequent research into SNV highlights the importance of long-term, specimen-based research. This rigorous approach to holistic specimen collection continues to stimulate integrated perspectives on the ecology and evolution of SNV years after the initial outbreak. 

Key Contributions 

  1. The diversity of hosts that might transmit hantavirus was efficiently screened, and deer mice (Peromyscus sonoriensis) were found to be the primary culprit. 
  2. Archived tissues that demonstrated the virus was not new, and not a pathogen that leaked from a research lab or released by the government. SNV was present in the earliest archived tissue samples from the MSB and Texas Tech University.
  3. Long-term study of the archive demonstrated the “Trophic Cascade Hypothesis,” with the emergence of SNV in human cases closely tied to El Niño weather events – where increased precipitation led to increased food for the primarily host reservoir, deer mice, larger rodent populations, and ultimately more contact with humans as these peridomestic rodents invaded homes and outbuildings.

Sin Nombre Hantavirus History

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“Mystery Flu Kills 6 in Tribal Area.” The first newspaper article published about the mystery illness. In consideration of deceased tribal individuals, their families, and cultural traditions, names have been redacted. May 27, 1993, Albuquerque Journal. 
 
In May 1993, cases of an unknown acute respiratory distress syndrome emerged in the Four Corners region. A young Navajo (Diné, “the people”) couple developed symptoms – shortness of breath, coughing, and fluid buildup in the lungs – and died days apart. Other young, healthy individuals exhibited the same symptoms, prompting local authorities to investigate. In the first year, the disease had a 50% mortality rate, killing 10 people in an eight week period.

Terry L. Yates, former curator of the MSB Division of Mammals, and his students assisted state and federal agencies in sampling potential vectors. The CDC identified it as a previously unknown hantavirus; at the time, hantaviruses known to infect humans had only been found in the Old World. Further analysis identified the Western deer mouse (Peromyscus maniculatus, now P. sonoriensis) as the primary reservoir, with viral sequences from patients matching those found in trapped mice.

deermouseculprit
Headline reads “Deer Mouse May Be Illness Culprit” by Rex Graham.
June 17, 1993, Albuquerque Journal.

 

Following the outbreak, Dr. Yates and other biologists at UNM sought to determine whether the virus was newly evolved or had been around longer. To test this question, researchers looked to museums, using archived tissue samples from the MSB and Texas Tech University. Between 1979 and 1992, there were 7,592 catalogued records in the MSB of these deer mice, many containing SNV. These samples, stored for decades before the outbreak, confirmed the virus was not “new,” but had gone undetected. Archived human autopsy samples showed that cases of Hantavirus in humans dated back to at least 1959. 

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Newspaper shows Jon Dunnum (now Collection Manager of the Division of Mammals) holding a deer mouse, while Mariel Campbell (now Collection Manager of the Division of Genomic Resources) looks at the mouse. September 24, 1996, Albuquerque Tribune.

 

During fieldwork, the MSB, CDC, and New Mexico Department of Health found higher rates of trap success in areas where SNV was reported – thus making the connection that a density of deer mice increased risk of human infection. The next question tied in greatly: did populations of P. maniculatus differ throughout the years? What was different about 1993, the first year that an outbreak was observed? 

Using data from the Sevilleta LTER, UNM investigators showed that El Niño wet weather led to a trophic cascade that increased food sources for deer mouse, causing their populations to explode. Unraveling the connection between pathogen emergence and El Niño weather was highlighted by the National Science Foundation on its 50th Anniversary as one of the Nifty 50 scientific discoveries.

As of 2022, there have been 864 confirmed cases of hantavirus since the CDC began monitoring in 1993, including those confirmed retrospectively. Despite the recent 30th anniversary of the outbreak, new research on Sin Nombre Hantavirus continues. Dr. Steven Bradfute, assistant professor at the UNM Center for Global Health and Department of Internal Medicine, leads a lab studying various emerging pathogens, including Sin Nombre. Recently, the Bradfute Lab has been conducting genetic analysis on wild-caught P. sonoriensis to understand why the virus is not found in eastern New Mexico.