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Update: Outbreak of Hantavirus Infection -- Southwestern United States, 1993

MMWR 42(23);441-443

Publication date: 06/18/1993

Table of Contents

Reported by




Numbered Of Confirmed Cases Of Hantivirus Illness


Since May 1993, the New Mexico Department of Health, the Arizona Department of Health Services, the Colorado Department of Health, the Utah Department of Health, the Indian Health Service (IHS), and CDC, with the assistance of the Navajo Nation Division of Health, have been investigating an outbreak of acute illness characterized by a prodrome most commonly including fever, myalgias, headache, and cough, followed rapidly by respiratory failure (1). Preliminary laboratory findings have suggested this outbreak is associated with infection with a hantavirus or a closely related agent. This report updates the ongoing investigation of this outbreak.

Because the findings in this investigation have suggested a role for hantavirus infection, the surveillance case definition has been revised. A confirmed case is now defined as unexplained adult respiratory distress syndrome (ARDS) or acute bilateral pulmonary interstitial infiltrates and/or prodromal symptoms in a person who had onset during 1993 and who has laboratory evidence of recent hantavirus infection. Through June 15, seven confirmed cases of hantavirus illness had been identified (Figure 1); four of these case-patients have died. Of the seven case-patients, four were from New Mexico, two from Arizona, and one from Colorado. Similar illnesses in an additional 22 persons, 12 of whom died, are being investigated.

Further laboratory studies have demonstrated the presence of hantavirus genome in autopsy specimens from two case-patients. Hantavirus-specific nucleotide sequences were amplified from specimens of organs using the polymerase chain reaction (PCR).

To characterize the preexistent seroprevalence of hantavirus antibodies among some persons in the area of the outbreak, serum samples collected in 1991 and 1992 as part of the Navajo Health and Nutrition Survey (CDC, unpublished data, 1991) were tested. Of samples obtained from 270 persons, antibodies to hantaviruses were present in specimens from three (1%) persons.

During the week of June 6, rodents were collected from peridomestic settings of several case-patients. Of 42 rodents tested, 12 (29%) had serologic evidence of hantavirus infection; all 12 were of the species Peromyscus maniculatus (deer mouse).

Since June 4, ribavirin has been available through an investigational new drug (IND) protocol to treat patients associated with this outbreak who have possible hanta-virus infection. Supplies of intravenous ribavirin have been placed in IHS and other facilities in the four-corners region of Arizona, Colorado, New Mexico, and Utah. Five patients have been enrolled in the IND protocol through June 15.

Reported by

F Koster, MD, H Levy, MD, G Mertz, MD, A Cushing, MD, S Young, PhD, K Foucar, MD, J McLaughlin, PhD, B Bryt, MD, Univ of New Mexico School of Medicine, T Merlin, MD, Lovelace Medical Center, Albuquerque; R Zumwalt, MD, P McFeeley, MD, K Nolte, MD, New Mexico Office of the Medical Investigator; MJ Burkhardt, MPH, Secretary of Health, N Kalishman, MD, M Gallaher, MD, R Voorhees, MD, M Samuel, DrPH, M Tanuz, G Simpson, MD, L Hughes, PhD, E Umland, MD, G Oty, MS, L Nims, MS, CM Sewell, DrPH, State Epidemiologist, New Mexico Dept of Health. R Levinson, MD, F Yerger, MD, B Allan, MD, Scottsdale; P Rubin, Phoenix; L Sands, DO, K Komatsu, MPH, C Kioski, MPH, K Fleming, MA, J Doll, PhD, C Levy, MS, TM Fink, P Murphy, B England, MD, M Smolinski, MD, B Erickson, PhD, W Slanta, G Gellert, MD, State Epidemiologist, Arizona Dept of Health Svcs. P Shillam, MSPH, RE Hoffman, MD, State Epidemiologist, Colorado Dept of Health. S Lanser, MPH, CR Nichols, MPA, State Epidemiologist, Utah Dept of Health. L Hubbard-Pourier, MPH, Div of Health, Navajo Nation, Window Rock, Arizona. J Cheek, MD, A Craig, MD, R Haskins, MPH, B Muneta, MD, B Tempest, MD, M Carroll, MD, LA Shands, MPH, JP Sarisky, MPH, RE Turner, L White, P Bohan, MS, Indian Health Svc. Div of Field Epidemiology, Epidemiology Program Office; National Center for Environmental Health; Div of Bacterial and Mycotic Diseases, Div of Vector-Borne Infectious Diseases, and Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases, CDC.


Editorial Note: Laboratory evidence continues to support an etiologic role of a hantavirus in the current outbreak of acute illness in the southwestern United States. The low prevalence of hantavirus antibodies in the recently collected nutritional survey specimens provides preliminary evidence that human hantavirus infections have occurred, but have been uncommon, in this population. The presence of hantavirus antibodies in the Peromyscus species will require further study to determine whether they were induced by the same virus associated with human infections (2,3).

In one controlled study, intravenous administration of the antiviral drug ribavirin was effective in treating severe cases of Hantaan virus infection when administered early in the course of illness (4). However, its effectiveness in the treatment of patients in the current outbreak has yet to be demonstrated; careful hemodynamic management and respiratory support are critical for possible case-patients. Patients eligible to receive ribavirin include previously healthy persons who reside in or have traveled to Arizona, Colorado, New Mexico, or Utah and who have acute (duration less than 7 days) unexplained ARDS or acute respiratory illness with bilateral pulmonary infiltrates on chest radiograph. Physicians wishing to enroll patients in the IND protocol should call, in New Mexico, (505) 843-2111; in Arizona, (602) 433-0215; or CDC, telephone (404) 639-3311.


  1. CDC. Outbreak of acute illness -- southwestern United States, 1993. MMWR 1993;42:421-4.
  2. LeDuc JW, Smith GA, Johnson KM. Hantaan-like viruses from domestic rats captured in the United States. Am J Trop Med Hyg 1984;33:992-8.
  3. Tsai TF, Bauer SP, Sasso DR, et al. Serological and virological evidence of a Hantaan virus- related enzootic in the United States. J Infect Dis 1985;152:126-36.
  4. Huggins JW, Hsiang CM, Cosgriff TM, et al. Prospective, double-blind, concurrent, placebo-controlled clinical trial of intravenous ribavirin therapy for hemorrhagic fever with renal syndrome. J Infect Dis 1991;164:119-27.


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Figure 1

Numbered Of Confirmed Cases Of Hantivirus Illness

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