Figure 1.

Diseases caused by Streptococcus pneumoniae. Pneumococci colonise the nasopharynx, evade host immunity and spread to the middle ear, sinus, lower respiratory tract, blood and meninges. Pneumococci cause otitis media in the middle ear, sinusitis in the sinus, pneumonia in the lower respiratory tract, bacteraemia in blood and meningitis in the meninges. The incidences of different types of pneumococcal infection are inversely related to the severity of disease: otitis media is the most common but the least severe. Redrawn and redesigned with permission from Ref. [2].