Plasmodium vivax malaria in the Republic of Korea during 2004-2005: changing patterns of infection.

Vivax malaria re-emerged in the Republic of Korea (ROK) in 1993. The annual incidence of this disease, which had increased rapidly through 2000 with geographic expansion, started to decrease in 2001, reaching 864 cases in 2004; however, the trends changed in 2005 when 1,304 cases were reported. Among 2,168 cases of vivax malaria reported from 2004 through 2005, 389 cases (17.9%) were ROK military personnel, 565 cases (26.1%) were veterans who had been discharged from the military within 2 years of report of infection, and 1,214 cases (56.0%) were civilians. Local transmission might have taken place during this period in the southern side of the Demilitarized Zone. Regional increase of vivax malaria in North Korea, increased local transmissions in ROK, and active transmission by vector mosquitoes during the transmission season might be important factors responsible for the re-increase of vivax malaria in ROK during 2005.