Epidemiological surveys and studies were made for 1,117 proved E.H. Fever patients at ARmy Epidemic Hemorrhagic Fever Research Team over the period of Jan. 1961 through Dec. 1964.
1) Attack rate per 1,000 of FROKA wara was 0.6-1.0 and 1.3 at central endemic zone.
2) Average case fatality rate was 12.6 percent. Higher fatality rate was showed on late spring outbreak than that of autumn.
3) Incubation period was between 8-32days. Average seemed to be longer than 20 days.
4) Entire FROKA area should be considered endemic of E.H. Fever. No change could be observed in the geographical localities throughout FROKA area.
5) Two outbreaks occurred over the year, one in May, Jung, July and another in October. November and December. Autumn outbreak was 3.3 times in average bigger than late spring outbreak in number
6) Fall outbreaks take place during dry months, ie, October, November and December. Spring epidemic also is preceded by a ralatively dry climate of April through May. However, no heavy rainfall of any duration can stop the outbreaks of E.H.Fever. Remakable is the fact that the sping peak in 1964 ceased to occur before the start of rainy season.
7) Most patinets develope in the temperature range of 10℃-25℃. Cases are observed even in the hottest season of a year and below zero.
8) Immuunologic phenomena could not be detected by epidemiological studies.
9) Chance of the exposure to the disease is not increased in a field exercise and works( compound and position).
10) 92.7 percent occurred as isolated event in terms of time and place and only 7.3% in group.
11) No specific type of terrain can be detected. but route of the infection seems not through the opening of the barrack.
12) Most of cases occur in the area of 150-250 meter above the sea level and one case was observed in 650 meter above the sea level.
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