Epidemic Survey of Epidemic Hemorrhagic Fever (Korean Hemorrhagic Fever) : With Particular Reference to Mode of Transmission of the Agent

Two clinical cases of epidemic hemorrhagic fever （or Korean hemorrhagic fever : KHF） occurred in the Animal Experiment Center of Sapporo Medical College between January and March, 1981. Investigation into the mode of transmission of the agent was carried out and the following results were obtained : 1） Based on the decision of the Committee of Prevention of KHF Epidemics all of the rats in this school were killed by anesthesia between February 7-14. At this time blood samples were taken randomly from the animals to examine the KHF antibody in sera. Blood sarmples were also collected from all of those taking care of the animals in the center and from researchers who had engaged in animal experiments and who had recently shown any symptoms suggestive of KHF. 2） The antibody examination disclosed that the antibody-positive rats were restricted to those animals kept in two out of three rat rooms in the center （infection rates of 28/34 and 2/6）, while animals kept in the facilities of individual departments in the school did not possess the antibody （0/15）. 3） Antibody-positive rates were calculated according to the body weight of the rats. The rates were 0% in animals of less than 200g, 88% in those of 200-300g, 67% in those of 300-400g, and 100% in those of more than 400g, indicating that most animals were infected with this agent during a relatively short period of time after entering this center. 4） All four animal care takers having the antibody were found to have participated in rearing the animals in the contaminated rat room. Two of these four were clinically severe and for one of these two the disease was fatal. 5） Of the five researchers with anamnesis of KHF-like symptoms, three were antibody-positive with two of them possessing relatively higher titers that were indicative of recent infection. 6） Based on the facts elicited in the incident in question, several items to be considered for preventing the outbreak of this disease were noted.