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Progress in the Development of Hantavirus Diagnostic Assays -- United States

Through September 29, 1993, a total of 39 persons in 11 states, including one recently identified in Montana, with confirmed acute hantavirus respiratory illness have been reported to CDC (1,2); 25 (64%) of these cases have been fatal. The diagnosis of confirmed hantavirus infection has been based on the presence in serum of immunoglobulin M (IgM) antibodies or rising titers of immunoglobulin G (IgG) antibodies that cross-react to four previously identified hantaviruses (Hantaan, Seoul, Puumala, and Prospect Hill), immunohistochemical staining of tissues, or a positive polymerase chain reaction (PCR) test in tissues.

Genetic recombinant-derived proteins have been produced in vitro from viral genomic sequences amplified from tissues obtained from patients who died with confirmed hantavirus illness. These proteins have been adapted to assays for homologous antiviral antibodies in patients with suspected hantavirus infection and in rodent hosts. At the University of New Mexico (UNM), Western blot assays with N and G1 proteins have been developed that successfully detected antibodies in serum from all 16 patients with confirmed disease who were tested; in nine of nine persons tested, antibodies were detected on the first day of hospital admission. The serum specimens did not react with the G1 proteins of Prospect Hill or Puumala viruses, the two hantaviruses that are most cross-reactive with the new hantavirus. No false-positive reactions occurred in 20 control serum specimens.

At CDC, purified recombinant N protein has been used as an antigen for IgG enzyme-linked immunosorbent assays (ELISAs) that demonstrated higher specific optical density values compared to Prospect Hill virus, the viral antigen previously identified as most reactive with serum specimens obtained from patients and rodents in the southwestern United States. Preliminary results with these ELISAs suggest that the use of homologous antigen may moderately increase the estimates of prevalence among infected rodents; no additional cases in humans have been recognized through the use of these assays. Negative tests on 232 serum specimens obtained from patients with adult respiratory distress syndrome not associated with hantavirus infections confirmed the specificity of the recombinant N protein antigen. Initial application of this same purified recombinant protein in IgM assays indicates that the protein is reactive in this format.

Reverse transcription and PCR amplification of genomic sequences from human blood obtained during the early phases of disease also has been attempted in collaborative studies between UNM and CDC. Stored peripheral blood mononuclear cells obtained early in the course of disease from seven patients with confirmed disease were PCR positive; four of the seven corresponding plasma specimens from these patients also were positive. All four stored blood clots available from these patients were positive as well.

Cases of acute hantavirus disease continue to be confirmed in the United States. The diagnostic findings of the prototypic tests described in this report suggest that it may be possible to rapidly diagnose infection in patients with suspected hantavirus disease. Use of recombinant-derived homologous antigens, which has preceded the isolation of the virus in cell culture, should improve the sensitivity and specificity of results obtained with available heterologous antigens. However, these hantavirus assays are for experimental use only and none have been approved by the Food and Drug Administration for use in the United States. These newer assays will require standardization and systematic evaluation with larger numbers of specimens before approval for marketing and broader usage are considered. Until assays are approved, health providers caring for patients with suspected hantavirus illness should forward specimens for testing to CDC through their respective state health departments. Reported by: B Hjelle, MD, S Jenison, MD, N Torrez-Martinez, Univ of New Mexico School of Medicine, Albuquerque. TA Damrow, PhD, State Epidemiologist, Montana State Dept of Health and Environmental Sciences. Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases, CDC.


  1. CDC. Update: hantavirus disease -- United States, 1993. MMWR 1993;42:612-4.

  2. CDC. Update: hantavirus-associated illness -- North Dakota, 1993. MMWR 1993;42:707.

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