Clinical and serologic responses of volunteers infected with phlebotomus fever virus (Sicilian type).

Twenty volunteers were inoculated with various doses of human serum containing Phlebotomus fever virus (Sicilian type) to determine their clinical and serologic responses as well as the human infectious dose50 of the virus. All infected subjects developed fever which varied in duration from 6 to 74 hours. The most common symptoms during sandfly fever were headache, anorexia, myalgia, photophobia, low back and retro-orbital pain. Infected individuals developed a marked leukopenia characterized by an initial lymphopenia followed by protracted neutropenia. Little complement fixing antibody was detected in convalescent sera but most subjects developed significant rises in hemagglutination inhibiting antibodies. All infected subjects developed specific neutralizing antibodies with titers ranging from 1:40 to 1:2,560. Of the three serologic tests performed, the plaque reduction neutralization method appears to be the most sensitive test for detecting antibodies to Phlebotomus fever viruses.