On May 14, 1993, the New Mexico Department of Health (NMDOH) reported it was notified by the Office of the Medical Investigator that two persons living in the same household had died within 5 days of each other.  Their illnesses were characterized by abrupt onset of fever, myalgias, headache, and cough, followed by the rapid development of respiratory failure. Tests for Yersinia pestis and other bacterial and viral pathogens were negative. After additional persons who had recently died following a similar clinical course were reported to the the NMDOH by the Indian Health Service (IHS), the ADHS, CDH, and UDH were contacted by the NMDOH seeking other possible cases.

Clinical and autopsy specimens are being processed and analyzed by the Centers for Disease Control and Prevention (CDC). Preliminary results include detection of rising titers of antibodies to hantaviruses in paired serum specimens from two of the nine case-patients; elevated single antibody titers were present in four other of the nine case-patients. The pattern of cross-reactivity to four different hantaviruses suggests that the infection is due to a previously unknown hantavirus. The NMDOH, ADHS, CDH, UDH, IHS, and CDC, with the assistance of the Navajo Nation Division of Health, are conducting intensive epidemiologic, laboratory, and environmental investigations to further define this unexplained illness cluster, determine the etiology of the illness, identify the source and mode of transmission, and develop prevention and control measures.

Rodents are the natural hosts for all known hantaviruses. Humans are thought to be at risk for infection after exposure to rodent excreta, either through the aerosol route or direct inoculation. There is no evidence of person-to-person transmission for any of the known hantaviruses, nor has occupational transmission been documented to health-care workers. Laboratory workers practicing universal precautions while processing routine clinical materials (such as blood, urine, and respiratory specimens) are not considered to be at increased risk for hantavirus infection. However, laboratory-acquired infections have occurred among persons who handled infected wild or laboratory rodents. Therefore, laboratory work that may result in propagation of hantaviruses should be conducted in a biosafety level 3 facility.