Table 1.

Pathogens commonly associated with pneumonia or acute lower respiratory tract infection in children less than 5 years of age^e

Age group	Bacteria	Viruses
<5 years	Streptococcus pneumoniae a Haemophilus influenzae a Mycoplasma pneumoniae b Staphylococcus aureus Klebsiella pneumoniae Streptococcus pyogenes Bordetella pertussis c Mycobacterium tuberculosis d	RSV Rhinovirus Influenza virus (A and B) Parainfluenza virus Human metapneumovirus Adenovirus Human corona virus
Neonates	Group B streptococcus Listeria monocytogenes Enteric (gram negative) bacteria Chlamydia trachomatis

RSV Respiratory Syncytial Virus, Staphylococcus aureus includes methicillin resistant strains (MRSA); Haemophilus influenzae includes type b and other encapsulated strains

^aDisease greatly reduced in settings with universal access to conjugated vaccines; ^bTypically considered as “atypical bacteria” requiring macrolide therapy; ^cmainly in unvaccinated babies, in older children it can present as a chronic cough; ^dThe risk of tuberculosis is dependent on the likelihood of Mycobacteria tuberculosis exposure/infection, which is a particular problem in areas with uncontrolled tuberculosis transmission

^eAdapted from [3, 6]