Ahead of Print -Hantavirus Infections among Overnight Visitors to Yosemite National Park, California, USA, 2012 - Volume 20, Number 3—March 2014 - Emerging Infectious Disease journal - CDC

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Ahead of Print -Hantavirus Infections among Overnight Visitors to Yosemite National Park, California, USA, 2012 - Volume 20, Number 3—March 2014 - Emerging Infectious Disease journal - CDC

Volume 20, Number 3—March 2014

Research

Hantavirus Infections among Overnight Visitors to Yosemite National Park, California, USA, 2012

Article Contents

• Methods
• Results
• Discussion
• Acknowledgments
• References
• Figure 1
• Figure 2
• Figure 3
• Figure 4
• Table
• Suggested Citation

Jonathan J. Núñez, Curtis L. Fritz, Barbara Knust, Danielle Buttke, Barryett Enge, Mark G. Novak, Vicki Kramer, Lynda Osadebe, Sharon Messenger, César G. Albariño, Ute Ströher, Michael Niemela, Brian R. Amman, David Wong, Craig R. Manning, Stuart T. Nichol, Pierre E. Rollin, Dongxiang Xia, James P. Watt, Duc J. Vugia , and for the Yosemite Hantavirus Outbreak Investigation Team

Author affiliations: California Department of Public Health, Richmond and Sacramento, California, USA (J.J. Núñez, C.L. Fritz, B. Enge, M.G. Novak, V. Kramer, S. Messenger, M. Niemela, D. Xia, J.P. Watt, D.J. Vugia); Centers for Disease Control and Prevention, Atlanta, Georgia, USA (J.J. Núñez, B. Knust, L. Osadebe, C.G. Albariño, U. Ströher, B.R. Amman, C.R. Manning, S.T. Nichol, P.E. Rollin); National Park Service, Fort Collins, Colorado, and Albuquerque, New Mexico, USA (D. Buttke, D. Wong)

Suggested citation for this article

Abstract

In summer 2012, an outbreak of hantavirus infections occurred among overnight visitors to Yosemite National Park in California, USA. An investigation encompassing clinical, epidemiologic, laboratory, and environmental factors identified 10 cases among residents of 3 states. Eight case-patients experienced hantavirus pulmonary syndrome, of whom 5 required intensive care with ventilatory support and 3 died. Staying overnight in a signature tent cabin (9 case-patients) was significantly associated with becoming infected with hantavirus (p<0.001). Rodent nests and tunnels were observed in the foam insulation of the cabin walls. Rodent trapping in the implicated area resulted in high trap success rate (51%), and antibodies reactive to Sin Nombre virus were detected in 10 (14%) of 73 captured deer mice. All signature tent cabins were closed and subsequently dismantled. Continuous public awareness and rodent control and exclusion are key measures in minimizing the risk for hantavirus infection in areas inhabited by deer mice.

Hantavirus pulmonary syndrome (HPS) is an acute viral disease, characterized by a nonspecific febrile illness followed by severe noncardiogenic pulmonary edema and cardiogenic shock. It is also referred to as hantavirus cardiopulmonary syndrome. Approximately 36% of reported HPS cases in the United States are fatal (1). HPS was first recognized in 1993 when an outbreak of unexplained respiratory deaths occurred among otherwise healthy adults in the southwestern United States (2–5). A previously unknown hantavirus, Sin Nombre virus (SNV), was identified as the etiologic agent (6,7). Deer mice (Peromyscus maniculatus) are the reservoir for SNV (8), which infected mice shed in their urine, saliva, and feces. Humans are exposed chiefly by inhaling aerosolized excreta. Activities associated with increased risk for HPS include occupying or cleaning rodent-infested buildings, sweeping or disturbing rodent excreta or nests, sleeping on the ground, and handling mice without gloves (9–11). Person-to-person transmission of SNV has not been documented (12).

During 1993–2011, a total of 587 cases of HPS were confirmed in the United States, primarily in western states (Centers for Disease Control and Prevention [CDC]/Viral Special Pathogens Branch, unpub. data). Although household clusters of HPS have been reported (13,14), most HPS cases occur as single, sporadic disease incidents. In August 2012, the California Department of Public Health (CDPH) confirmed HPS in 2 California residents, both of whom had visited Yosemite National Park (Yosemite) in June 2012 and had lodged in so-called signature tent cabins (which differ from regular tent cabins by having an interior wall and roof consisting of drywall with a layer of foam insulation between the drywall and exterior canvas) in the Curry Village area of Yosemite Valley. Because of the common travel history of these otherwise nonepidemilogically unrelated patients, CDPH, in collaboration with CDC, the National Park Service (NPS) Office of Public Health, and others, initiated an investigation of a possible HPS outbreak associated with Yosemite. This report summarizes the clinical, epidemiologic, laboratory, and environmental findings of the investigation.

Dr Nunez is a physician and was an Epidemic Intelligence Service officer at CDC assigned to CDPH. His research interests focus on infectious diseases and public health. He is currently an infectious disease fellow at the University of Pennsylvania in Philadelphia.

Acknowledgments

We thank the physicians and laboratory staff members who tested samples from suspected case-patients and reported patients who had initial positive test results, staff of local and state health departments who facilitated follow up of suspected and confirmed case-patients, and various media groups for broadcasting news of the outbreak to the general public. We also thank the Delaware North Corporation for their cooperation with the investigation.

In addition to this article’s authors, members of the Yosemite Hantavirus Outbreak Investigation Team include the following: CDPH: Marco Metzger, Joseph Burns, Sarah Billeter, Larry Bronson, Debra Wadford, David Cottam, Jason Wilken, Rebecca Jackson, Rachel Roisman, Barbara Materna, Dina Dobraca, Tracy Barreau, Heather Bourbeau, Anita Gore, Gilberto Chavez; CDC: Shelley Campbell, Deborah Cannon, Aridth Gibbons, Zachary Reed, Lisa Wiggleton Guerrero, Katrin Kohl, Sherif Zaki, Dianna Blau, Kristy Gerdes; NPS: Don Neubacher, Matthew Weinburke, Woody Smeck, Adam Kramer, Charles Higgins, Chris Lehnertz; Pennsylvania Department of Health: Andre Weltman; and West Virginia Department of Health: Rachel Radcliffe.

Animal handling techniques were performed under the California Department of Public Health US Department of Agriculture research institution certificate no. 93-R-0551, approved animal care and use protocol #2012-14.

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Figures

• Figure 1. . Dates of stay in Yosemite National Park (Yosemite), incubation periods, and dates of illness onset for 10 case-patients, 2012. Incubation period calculated as days from last date of...
• Figure 2. . Regular and signature tent cabins, Yosemite National Park, summer, 2012. A) Outside view of a regular tent cabin. B). Outside view of a signature tent cabin. C) Inner...
• Figure 3. . Inside view of regular and signature tent cabins, Yosemite National Park, summer 2012. A) Regular tent cabin showing canvas affixed over a wood frame. B) Signature tent cabin...
• Figure 4. . Damage from rodents tunneling in the foam insulation of a signature tent cabin, Yosemite National Park, summer 2012.

Table

• Table. Clinical characteristics of 10 hantavirus case-patients who were exposed at Yosemite National Park, 2012

Suggested citation for this article: Núñez JJ, Fritz CL, Knust B, Buttke D, Enge B, Novak MG, et al. Hantavirus infections among overnight visitors to Yosemite National Park, California, USA, 2012. Emerg Infect Dis [Internet]. 2014 Mar [date cited]. http://dx.doi.org/10.3201/eid2003.131581

DOI: 10.3201/eid2003.131581

1Members of the Yosemite Hantavirus Outbreak Investigation Team are listed at the end of the article.