Since LACV replicated to high titers in the nasal turbinates, we sought to determine if intranasal inoculation of mice with LACV could lead to infection. Three-weekold Swiss Webster weanling mice (n = 6/dose) were inoculated intranasally (IN) (10 µl volume) or intraperitoneally (IP) (100 µl volume) with serial dilutions of LACV/ human/1960, and the LD 50 and 50% infectious dose (ID 50 ) were determined. Clinical disease served as a surrogate for lethality and mice were promptly euthanized prior to succumbing to LACV disease. In both groups, clinical disease was first noted on day 6 ( Figure 3 ). Twenty days post-inoculation, the LD 50 was determined. All surviving mice were tested for the development of a neutralizing antibody response. respectively) were slightly lower than the LD 50 titers, indicating LACV can cause a subclincal infection in weanling mice, but only at low doses.