Pneumococcal disease is an infection caused by the Streptococcus pneumoniae (S. pneumoniae) bacterium, also known as pneumococcus. Infection can result in pneumonia, infection of the blood (bacteremia/sepsis), middle-ear infection (otitis media), or bacterial meningitis.
The World Health Organization (WHO) says that pneumococcal disease is the world’s number 1 vaccine-preventable cause of death among infants and children younger than 5 years of age.
There are two main types of pneumococcal diseases:
1) Non-invasive pneumococcal diseases
These may be less serious than invasive pneumococcal disease and occur outside the major organs or the blood. S. pneumoniae can spread from the nasopharynx (nose and throat) to the upper and lower respiratory tract and can cause:
- Otitis media – middle ear infection. Inflammation of the middle ear, typically with accumulation of fluid in the middle ear, swelling of the eardrum, earache. If the eardrum is perforated drainage of pus into the ear canal.
- Non-bacteremic pneumonia – infection of the lower respiratory tract without detectable spread of organisms to the blood stream
2) Invasive pneumococcal diseases (IPD)
These tend to be more serious and occur inside a major organ, or in the blood. Examples of IPDs include:
- Bacteremia (sepsis) – bacterial infection of the blood. Bacteremia refers to the presence of live bacteria in the blood, while sepsis means a blood infection which is associated with capillary leak, shock and an increased risk of mortality.
- Meningitis – inflammation of the meninges. The meninges are the three membranes that cover the brain and the spinal cord.
- Bacteremic pneumonia – inflammation of one or both lungs, with pneumococcus in the bloodstream.
Pneumococcal Disease Burden
According to the WHO, up to 1.6 million people die each year globally as a result of pneumococcal diseases – about half of them are children younger than 5 years of age in developing countries. WHO classes pneumococcal disease as a major cause of mortality and morbidity.
(Morbidity = illness, disease. Mortality = death).