Isozyme analysis (12 enzymes: 14 loci) was conducted on 99 isolates of Trypanosoma cruzi: 77 from Guatemala, 5 from
Mexico and 17 from South American countries. Analyses of 4 population-genetic indices were undertaken to assess the
possibility of genetic exchange occurring among Guatemalan isolates. The results provide evidence for a degree of genetic
exchange occurring among isolates from this relatively small geographical area. Previous studies of population genetics
on T. cruzi might have failed to detect this phenomenon because they tended to use isolates originating far from one
another, rendering gene exchange unlikely for geographical reasons. Phylogenetic data, presented here, show considerable
differences in genetic structure between Central and South American isolates, suggesting that different biological and
clinical properties might be expected. For example, there are differences in clinical syndromes between Central and South
America, a situation discussed further here.