Leptospirosis in the Philippines. 
Leptospirosis was first isolated in the Philippines from one of the human cases of Weil's Disease in 1932 and from then up to 1970 a total of 65 cases were studied sporadically.  From 1971 up to 1973 a total of 390 cases were studied out of which 82 (21.02%) were found positive by isolation and serological examination.  An outbreak of leptospirosis was followed up from 1976 to 1983 in a penal farm in Sablayan, Mindoro.  At the time of the outbreak, 31% of the sera from patients and those with complaints reacted to one or more antigen pools with 40% of these reactors reacting to only one antigen pool.  Only one percent of prisoners and residents without complaints reacted to one or more antigen pools, with 80% of these reactors reacting to pool 3 alone.  Three and half years later, a first follow-up was done in which 9.07% reacted to one or more pools.  Of these, 42% reacted to pool 2 and 82% to pool 3 alone or in combination with other pool.  Ninety five percent of those reacting to Pool 2 reacted to L. pyrogenes and 88% of those that reacted to Pool 3 reacted to L. autumnalis.  More than three years later after the first follow-up, a second follow up was done.  This time 2.29% reacted to one or more pools.  Most reacted specifically to L. autumnalis.  The residents outside the penal farm were all non-reactive.  Sampling from another penal colony and in four agricultural areas revealed no significant reactivity.(ABSTRACT TRUNCATED AT 250 WORDS)