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A summary of CDC's clinical overview for healthcare providers.
- Streptococcus pneumoniae causes pneumococcal disease.
- Certain ages and conditions raise the risk.
- Vaccination is recommended to prevent it.
The organism
S. pneumoniae are lancet-shaped, gram-positive, facultatively anaerobic bacteria with more than 100 known serotypes. Most serotypes can cause disease, but a minority cause most infections.
Carriage
Pneumococci commonly live in the respiratory tract. They can be isolated from the nasopharynx of 5–90 percent of healthy people, depending on the population and setting:
| Group | Share who may be carriers |
|---|---|
| Adults without children | 5–10% |
| School-aged children | 20–60% |
| Service members on military installations | 50–60% |
Carriage generally lasts longer in children than in adults. How carriage relates to natural immunity is not clearly understood.
Who is at higher risk
Age: children under 5 and adults 50 or older.
Conditions and other factors that raise the risk of invasive disease:
- alcoholism;
- cerebrospinal fluid leak;
- chronic heart, kidney, liver or lung disease — including chronic obstructive pulmonary disease, emphysema and asthma;
- cigarette smoking;
- a cochlear implant — which appears to raise the risk of pneumococcal meningitis specifically;
- an immunocompromising condition;
- diabetes.
Immunocompromising conditions include chronic kidney failure or nephrotic syndrome; congenital or acquired asplenia or splenic dysfunction; congenital or acquired immunodeficiency; HIV infection; sickle cell disease and other haemoglobinopathies; and diseases treated with immunosuppressive drugs or radiation, including Hodgkin disease, leukaemias, lymphomas, malignant neoplasms and solid organ transplant.
Racial and ethnic groups. For reasons experts do not know, rates are higher among Alaska Native people, African American people and certain American Indian people.
Close contact. Crowded settings, such as childcare and nursing homes, and certain living conditions, such as homelessness, raise the risk.
How it spreads
S. pneumoniae spreads person to person through respiratory droplets. The serotypes that most often cause infection are the ones most often carried; carriage does not always lead to disease, but it is an important precursor.
Spread within a household is influenced by crowding, the presence of upper respiratory infections or pneumococcal disease, and the season.
How long someone is contagious is unknown; presumably, as long as the organism is in respiratory secretions.
Clinical features
| More serious | Less serious, more common |
|---|---|
| pneumonia, bacteraemia, meningitis | acute otitis media, sinusitis |
Prevention
Vaccination is the primary way to prevent pneumococcal disease.
Testing and diagnosis
A definitive diagnosis generally relies on isolating the organism from a normally sterile site. Other tests are available, such as a urinary antigen test for the C-polysaccharide antigen of S. pneumoniae, and culture-independent molecular methods.
Surveillance
CDC monitors rates of invasive pneumococcal disease in the United States through two surveillance systems.
Sources
- Centers for Disease Control and Prevention, "Clinical Overview of Pneumococcal Disease." https://www.cdc.gov/pneumococcal/hcp/clinical-overview/index.html
- Further reading: the pneumococcal disease chapter of CDC's Pink Book; CDC's clinical guidance; and the PneumoRecs VaxAdvisor app.
- Rewritten in hubnx's own words.
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