False-colour transmission electron micrograph of whooping cough bacteria, Bordetella pertussis. The micrograph shows the genetic material (DNA) of the bacteria as blue regions within the cell. The whooping cough bacterium parasitises only humans. It causes a respiratory tract infection characterised by fits of coughing that end in loud inspiratory whoops. The infection is usually contracted in childhood and is potentially fatal in infancy. Adults are sometimes affected. Magnification: x15,600 at 6x4.5cm size.