Re-emerging Plasmodium vivax malaria in the Republic of Korea

Abstract

Plasmodium vivax malaria, which was highly prevalent in the Republic of Korea, disappeared rapidly since 1970s. However, malaria re-emerged with the first occurrence of a patient in 1993 near the demilitarized zone (DMZ), the border between South Korea and North Korea. Thereafter, the number of cases increased exponentially year after year, totaling 6,142 cases (6,249 if United States Army personnels were included) by the end of 1998. Interestingly enough, the majority of cases (3,743; 61%) was soldiers aged 20-25, camping around the northern parts of Kyonggi-do or Gangwon-do (Province) just facing the DMZ. Among 2,399 civilian cases, 1,144 (47.7%) were those who have recently retired from their military services in the northern parts of the two Provinces. The re-emerging malaria characteristically revealed a combination type of short and long incubation periods with predominance of the long type. The course of illness was relatively mild, and the treatment was successful in most patients. Vector mosquitoes are Anopheles sinensis and possibly A. yatsushiroensis. Wide-scale preventive and control measures should be operated to eradicate this re-emerging disease. It has been suggested by many authors that the initial source of the re-emerging malaria was infected mosquitoes which had flown from the northern part of the DMZ.

Fig. 1

Malaria (Plasmodium vivax) situation in 1965. Note that the residual endemic areas were Kyongsangbuk-do (Province) (A) especially northern parts and Kyonggi-do (B) especially northern and southeastern parts. (Reproduced from Ministry of Health and Social Affairs, Korea, 1966).

Figs. 2-3

A ring form (Fig. 2) and a gametocyte (Fig. 3) of Plasmodium vivax found from the first case of the re-emerging malaria in 1993 (Chai et al., 1994).

Fig. 4

Explosively increasing numbers of re-emerging malaria cases among the Korean people by the end of 1998.

Fig. 5

Re-emerging malaria in the Republic of Korea (1994-1997), showing the major outbreak areas, northern parts of Kyonggi-do (A) and Gangwon-do (B), and a tendency of expanding southwards and eastwards. The majority of cases found in areas remote from the two Provinces (A and B) were veterans recently retired from military services in the outbreak areas.

Fig. 6

Recent situation of the re-emerging malaria in 1998. The major outbreak areas were still confined to the northern parts of Kyonggi-do and Gangwon-do. However, many patients occurred in remote areas also. It seems that they consisted of both veterans recently retired from military service in the outbreak areas and locally transmitted cases.

Fig. 7

Seasonal incidence of malarial attacks in the Republic of Korea in 1913 (Hasegawa, 1913) and in 1993-1996 (Chai, 1997). The seasonal patterns are very similar each other.

Fig. 8

Typical fever patterns of the re-emerging P. vivax malaria. A. The first case found in 1993 (Chai et al., 1994). B. Another case detected in 1994 (Seo et al., 1995).