A large epidemic of leptospirosis was anticipated in September 1990 because flood has resulted the heavy rain for 4 consecutive days from the 8th of September, 1990, in the Yang-pyeung Gun(County), a farm area of Central Korea. Actually, patients
were
already appearing sporadically soon after the flood. Soldiers of ROK Army units stationed in this area were under the higher risk since many of them participated in field works(such as tieing rice plant fallen by the flood) as a part of Civil Aid
Plan.
The objectives of this study were 1) to detect infected ones at early stage 2) to estimate the attach rates of infection and apparent infection through seologic examination. 3) to estimate pathogenecity and case-fatality rate and 4) to compare
the
rates
of infection by the type of work and the use of protective devices.
All of those with febrile episode were interviewed and the leptospiral antibody was examined during the one month period after the field work. Serologic examinations(including the interview) were done twice with 1 week interval(first on 8th to
10th
of
October, about 4 weeks following the days of field work) for 446 soldiers belong to three companies stationed in the county area. The serologic test(Microscopic) agglutination test) were performed with 4 strains, leterchemorrhagiae lai and
Canicola
canicale Hond Utrecht IV as standard strains, and 6P-0.49-1 and YP-35-1 as strains isolated in Korea in 1986, in accordance with WHO guideline.
@ES The results are as follow.
@EN 1. Among 57 febrile, suspected cases. 37 had serological tests twice and, 20 of them (54.1%) were serologically confirmed to be infected whereas among other 20 subjects who had single serological test, only 2 persons(10.0%) were serologically
positive.
2. The dates of onset of fever in confirmed cases were clustered in 10 to 20 days from late September to early October, which coincided well with the duration of exposure(Sep. 13-18).
3. The attack rate of infection and apparent infection were estimated to be 11.2%(95% C.I. :8.3-14.1%). 1.8%(95% C.I. :0.7-3.1%). Pathogenecity and case-fatality rate were estimated to be 16.0%(95% C.I.: 6.0-26.0%) and 0%, respectively.
4. The attack rate of infection of persons who worked in rice paddy for 3-6 days, for 1-2 days and participated in other field work were 3.5, 2.7 and 2.1 time high respectively as high as that of persons who did not join in field work (p<0.05).
5. The effectiveness of protective devices shown in this study was rather poor; perhaps the preparation of the protective devices was not sufficient because the mobilization of army is usually a sudden order. For more satisfactory prevention in
the
future, a complete clothing(including glove and boots) and chemoprophyaxis(with doxicycline0 are recommended.
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