Armstrong – Table of Contents

major phylogenetic and antigenic groups corresponding to 1) LCM, Lassa and close
relatives in association with Old World Rodents, (family Muridae, subfamily Murinae)
and 2) the Tacaribe complex from the New World or American Rodents (family Muridae,
subfamily Sigmodon tinaie). The correspondence between the phylogeny of the hosts and
viruses suggest a long-associated co-evolution. The New World viruses, derived from
clinical cases were isolated as follows: Jumin, 1958, Machupo, 1963, Lassa, 1969,
Guarnarito, 1989, and Sabia viruses, 1990. For details of virus characterization,
molecular virology, and clinical manifestations, consult recent editions of texts on
virology (43) or clinical infectious diseases (44).
At present LCM is considered to be frequent as determined by the prevalence of
antibodies in persons without prior history of illness. Clinical illness is infrequent. Most
recognized cases occur in the autumn when rodents seek indoor shelter and are associated
with rodent infestation. The usual pathway of infection is by the aerosol route. Cases
have occurred in association with rodents such as mice, hamsters or guinea pigs often
acquired from pet shops. Occasionally dogs may harbor the virus. There have been
laboratory outbreaks as described. Recently LCM has been transmitted by tissue
transplantation from asymptomatic individuals (45, 46).
In December 1996, Dr. Robert M. Chanock , Chief, Laboratory of Infectious
Diseases (LID), NIH wrote as follows in his review (47) of LID for the Board of
Scientific Counselors in the section Long Term Research Goals and Readjustment of
Specific Approaches in Response to Technological Advances: “Despite many
temptations to limit study to smaller and smaller model systems of infection, the research
goals of LID have remained the same, namely 1) delineation of the etiology,