Three cases of laboratory infection with the virus of Rift Valley fever are recorded. The more prominent subjective symptoms and the course of the illness in each case have been briefly described. The incidence of these infections under the circumstances noted indicates that the virus is highly infectious for man.
The neutralization test as herein performed on the sera of convalescents, and the use of the mouse for infectivity tests provide satisfactory aids in establishing a diagnosis.
Desiccation of serum-virus in vacuo while in the frozen state is an efficient means of preserving the activity of the virus over relatively long periods of time.
The blood of mice sick with Rift Valley fever may contain at least ten billion infective doses of virus, for mice, per cubic centimeter.
The infectivity of the virus of Rift Valley fever for mice is lost after appropriate exposure to methylene blue in the presence of light. Following an optimal degree of such treatment, the inactivated virus may retain some degree of immunizing power.