Hantavirus Pulmonary Syndrome -- United States, 1993

In June 1993, a newly recognized hantavirus was identified as the etiologic agent of an outbreak of severe respiratory illness (hantavirus pulmonary syndrome {HPS}) in the southwestern United States (1-3). Since this problem was recognized, sporadic cases have been identified from a wide geographic area in the western United States (2). This report summarizes the epidemiologic characteristics of HPS cases reported to CDC from May 1 through December 31, 1993.

Through December 31, 53 persons with illnesses meeting the surveillance case definition of HPS (2) have been reported to CDC. Patients' ages have ranged from 12 years to 69 years (median age: 31 years), and 32 (60%) were aged 20-39 years; 30 (57%) were male. Twenty-six (49%) were American Indians; 22 (42%), non-Hispanic whites; four (8%), Hispanic; and one (2%), non-Hispanic black. Thirty-two (60%) patients died; persons with fatal cases and persons with nonfatal cases were similar in age, sex, and race (Table_1).

Cases have occurred in residents of 14 states (Figure_1). Of the 34 (64%) persons who were residents of Arizona, Colorado, or New Mexico, illness occurred in 25 (74%) during April-July 1993 and in one before 1993 (Figure_2). In comparison, of 19 cases reported from other states, five (26%) had onset of illness during April- July 1993, and seven (37%) had onset before 1993. All patients either lived in rural areas or had visited rural areas during the 6 weeks before onset of illness.

The etiology of HPS was initially identified by serology, polymerase chain reaction (PCR), and immunohistochemistry (2). Additional cloning and sequencing of virus ribonucleic acid (RNA) from human autopsy tissues indicated that all three of the RNA segments of this new virus were unlike those of any known hantavirus; the new hantavirus is most closely related to the Prospect Hill strain of hantavirus (4,5).

In November 1993, the etiologic hantavirus associated with HPS was isolated from tissues of a deer mouse (Peromyscus maniculatus) trapped in New Mexico in June 1993 near the residence of a person with confirmed HPS. Lung material from this animal was twice passed in uninfected laboratory deer mice and then adapted to Vero E6 cell cultures. The genetic sequence of the 139-nucleotide PCR product from the isolated virus was identical to PCR products amplified from this rodent in June 1993 and from lung tissue of the associated patient. At the same time, the U.S. Army Medical Research Institute of Infectious Diseases isolated the virus from specimens from a person in New Mexico and from a rodent in California. Muerto Canyon virus has been proposed as the name for this virus, following standard conventions for naming zoonotic viruses after a nearby geographic feature. Reported by: L Sands, DO, State Epidemiologist, Arizona Dept of Health Svcs. GW Rutherford, III, MD, State Epidemiologist, California Dept of Health Svcs. RE Hoffman, MD, State Epidemiologist, Colorado Dept of Health. E Sfakianaki, MD, Dade County Public Health Unit, RS Hopkins, MD, State Epidemiologist, Florida Dept of Health and Rehabilitative Svcs. R Perotto, MS, Acting State Epidemiologist, Div of Health, Idaho Dept of Health and Welfare. ML Fleissner, DrPH, State Epidemiologist, Indiana State Dept of Health. D Alfano, Kansas Dept of Health and Environment. L McFarland, DrPH, State Epidemiologist, Office of Public Health, Louisiana Dept of Health and Hospitals. MT Osterholm, PhD, State Epidemiologist, Minnesota Dept of Health. TA Damrow, PhD, State Epidemiologist, Montana State Dept of Health and Environmental Sciences. A DiSalvo, MD, State Health Laboratory, Div of Health, Nevada State Dept of Human Resources. CM Sewell, DrPH, State Epidemiologist, New Mexico Dept of Health. LA Shireley, MPH, State Epidemiologist, North Dakota State Dept of Health and Consolidated Laboratories. D Fleming, MD, State Epidemiologist, State Health Div, Oregon Dept of Human Resources. KA Senger, State Epidemiologist, South Dakota State Dept of Health. DM Simpson, MD, State Epidemiologist, Texas Dept of Health. US Army Medical Research Institute of Infectious Diseases, Frederick, Maryland. Hantavirus Task Force, Special Pathogens Br, Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: New clinical syndromes and infections associated with previously unknown pathogens often are recognized only after clinicians and public health officials become aware of clusters of cases. In May and June 1993, the recognition and reporting of 24 cases of severe respiratory illness among residents of the southwestern United States led to a multiagency response that included state and local health departments, universities, the Indian Health Service, the Navajo Nation Division of Health, and CDC. This response, in turn, resulted in the identification of HPS.

Disease associated with hantaviruses occurs primarily in otherwise healthy adults; however, HPS affects both sexes while infection by other hantaviruses affects predominantly males (6,7). The case-fatality rate for persons infected with Muerto Canyon virus has been substantially (more than 10 times) higher than that for persons infected with other hantaviruses (8). Factors accounting for the seasonal pattern of HPS have not been fully defined.

Although all confirmed cases of HPS in 1993 occurred in persons who resided west of the Mississippi River, the primary reservoir of the virus, the deer mouse, inhabits all areas of the United States except the southeast and Atlantic seaboard (9). Since January 1, 1994, one case of HPS has been confirmed in a resident of Indiana, and a possible case is under investigation in Florida. Regional variations in the occurrence of this problem and observed differences in the racial/ethnic and age distribution may reflect differences in 1) activities associated with exposure or transmission, 2) local surveillance and retrospective case finding, or 3) the prevalence of the virus in the rodent host. For example, persons participating in agricultural activities near habitats of infected rodents are likely to be at greater risk for infection.

Recognition of the more geographically widespread occurrence of HPS emphasizes the need for physicians and other health-care providers to consider this problem in the differential diagnosis of adult respiratory distress syndrome. CDC and state and local health departments request that suspected cases of HPS be reported through state health officials (2).

The isolation of Muerto Canyon virus and the development of recombinant proteins may enable improved and more rapid diagnostic testing. CDC and the Association of State and Territorial Public Health Laboratory Directors are organizing training courses on hantavirus testing for public health laboratory personnel. The first course for public health laboratory personnel from states with confirmed cases of HPS will be conducted in Atlanta March 7- 10, 1994. A purified recombinant necleoprotein antigen expressed in Escherichia coli (10) will be made available to participants and, as supplies permit, other interested laboratories. Additional information regarding these courses is available from CDC's Public Health Practice Program Office, telephone (404) 488-7675.

References

1. CDC. Outbreak of acute illness -- southwestern United States, 1993. MMWR 1993;42:421-4.

2. CDC. Update: hantavirus pulmonary syndrome -- United States, 1993. MMWR 1993;42:816-20.

3. Nichol ST, Spiropoulou CF, Morzunov S, et al. Genetic identification of a hantavirus associated with an outbreak of acute respiratory illness. Science 1993;262:914-8.

4. Spiropoulou CF, Morzunov S, Feldmann H, Sanchez A, Peters CJ, Nichol ST. Genome structure and variability of a virus causing hantavirus pulmonary syndrome. Virology 1994 (in press).

5. Hjelle B, Jenison S, Torrez-Martinez N, et al. A novel hantavirus associated with an outbreak of fatal respiratory disease in the southwestern United States: evolutionary relationships to known hantaviruses. J Virol 1994;68:592-6.

6. Feldmann H, Sanchez A, Morzunov S, et al. Utilization of autopsy tissue RNA for the synthesis of the nucleocapsid antigen of a newly recognized virus associated with hantavirus pulmonary syndrome. Virus Res 1993;30:351-67.

7. Xu ZY, Guo CS, Wu YL, Zhang XW, Liu K. Epidemiologic studies of hemorrhagic fever with renal syndrome: analysis of risk factors and mode of transmission. J Infect Dis 1985;152:137-44.

8. Korpela H, Lahdevirta J. The role of small rodents and patterns of living in the epidemiology of nephropathia epidemica. Scand J Infect Dis 1978;10:303-5.

9. McKee KT Jr, LeDuc JW, Peters CJ. Hantaviruses. In: Belshe RB, ed. Textbook of human virology. 2nd ed. St. Louis: Mosby Year Book, 1991:615-32.

10. Hall RE. Peromyscus maniculatus. In: Mammals of North America. 2nd ed. New York: Wiley, 1981:670-83.

+------------------------------------------------------------------- ------+ | Erratum: Vol. 43, No. 3 | |             | | SOURCE: MMWR 43(07);127 DATE: Feb. 25, 1994 | |             | | In the article "Hantavirus Pulmonary Syndrome -- United States, | | 1993," on page 48, some references were misnumbered. Reference 6 | | should be numbered 10, and references 7, 8, 9, and 10 should be | | numbered 6, 7, 8, and 9, respectively. | |             | +------------------------------------------------------------------- ------+
Table_1
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TABLE 1. Characteristics of 53 persons reported with hantavirus pulmonary syndrome,
by outcome -- United States, May-December, 1993
=====================================================================================
                                        Deaths
                                     -------------
Characteristic           Total       No.      (%)     Relative risk   (95% CI*)
--------------------------------------------------------------------------------
Age (yrs)
    <20                     7          4      (57)      Referent
  20-29                    14          7      (50)        0.9         (0.4-2.0)
  30-39                    18         14      (78)        1.4         (0.8-2.7)
   >=40                    14          7      (50)        0.9         (0.4-2.0)

Sex
  Female                   23         13      (57)      Referent
  Male                     30         19      (63)        1.1         (0.7-1.8)

Race
  American
   Indian                  26         15      (58)      Referent
  Other+                   27         17      (63)        1.1         (0.7-1.7)
--------------------------------------------------------------------------------
* Confidence interval.
+ Non-Hispanic white, Hispanic, and non-Hispanic black.
=====================================================================================

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