Seasonal distribution of Legionella spp. and L. pneumophila in a river in Taiwan evaluated with culture-confirmed and direct DNA extraction methods

•Seasonal distribution of Legionella ranged from 34.3% in winter to 58.8% in spring.•Seasonal density of Legionella ranged from 1.9×102 in fall to 7.1×103CFU/L in spring.•Direct DNA extraction method may be more suitable for detecting Legionella spp.•Culture-confirmed method may be more sensitive for detecting L. pneumophila.