 However, estimates using newer polymerase chain reaction-based diagnostic techniques indicate that prevalence is probably grossly underestimated.In one study from the 1980s, a prevalence of over 90% was found in persons greater than 10 years old in a small village near Khon Kaen in northeast Thailand in the region known as Isaan.Sporadic cases have been reported in case reports from Malaysia, Singapore, and the Philippines.