**5.14. Co-infections**

Co-infection Infections involving both respiratory bacteria and viruses or are common. Viral infection usually occurs first, followed by a secondary bacterial infection, as observed in the influenza pandemics of 1918, 1957, and 1968 where most deaths occurred due to secondary bacterial infection. In some infections however, especially H5N1 avian influenza, the associated pneumonia appears to be caused by direct viral action.

Co-infections are particularly common in 45% of children with CAP, and mainly involve pneumococcus [66], Mycoplasma pneumoniae and several species of *Chlamydophila*. CAP of mixed etiology has been characterized less in adults than in children, and prevalence is estimated at less than 5%. The most common combinations reported are pneumococcus with rhinovirus or influenza A virus [67].
