Pneumococcal Disease: Causes and How It Spreads

Key Points

  • Streptococcus pneumoniae bacteria can cause infections called pneumococcal disease.
  • The bacteria spread through direct contact with respiratory secretions.
  • A person's risk can vary due to many factors.
A man coughing


Pneumococcal disease is a name for any infection caused by bacteria called Streptococcus pneumoniae, or pneumococcus.

A computer-generated image of Streptococcus pneumoniae based on scanning electron microscopic imagery.
This image of Streptococcus pneumoniae was computer generated.

How the bacteria spread

People spread pneumococcal bacteria to others through direct contact with respiratory secretions, like saliva or mucus.

Many people, especially children, have the bacteria in their nose or throat at one time or another without being ill. Experts call this "carriage," and it only rarely leads to sickness.

Risk factors

Age, conditions, and other factors can increase someone’s risk for pneumococcal disease, including severe infections.


Children younger than 5 years old and adults 65 years or older are at increased risk for pneumococcal disease.

Race and ethnicity

Experts don't know why, but people of certain racial and ethnic groups have increased rates of pneumococcal disease:

  • Alaska Native people
  • African American people
  • Certain American Indian people

Childcare attendance

Young children attending childcare are also at increased risk for severe pneumococcal disease and ear infections.

Medical conditions

Chronic conditions and other factors that increase someone's risk for pneumococcal disease include:

  • Alcoholism
  • Cerebrospinal (around the brain and spinal cord) fluid leak
  • Chronic heart, kidney, liver, or lung disease
  • Cigarette smoking
  • Cochlear implant (surgically implanted hearing device to help people with severe hearing loss)
  • Diabetes
  • Immunocompromising condition (having a weakened immune system)

Chronic lung disease includes chronic obstructive pulmonary disorder (COPD), emphysema, and asthma.

Immunocompromising conditions that increase someone's risk for pneumococcal disease include:

  • Damaged spleen or having no spleen
  • Disease or condition that weakens the immune system
  • Disease or condition treated with medicine that weakens the immune system*
  • HIV infection
  • Kidney failure requiring maintenance dialysis or nephrotic syndrome (a kidney disorder)
  • Sickle cell disease or other inherited blood disorders

*This includes cancer and solid organ transplant