Pneumococcal disease is caused by Streptococcus pneumoniae, a bacterium that has more than 100 serotypes. Most serotypes cause disease, but only a few produce the majority of invasive pneumococcal disease.
Ask the Experts: Pneumococcal: Disease Issues
The disease is spread from person to person by droplets in the air. The pneumococci bacteria are common inhabitants of the human respiratory tract. They may be isolated from the nasopharynx of 5%–90% of healthy people.
There are two major clinical syndromes of invasive pneumococcal disease: bacteremia (blood stream infection), and meningitis (infection of the meninges that surround the brain). They are both caused by infection with the same bacteria, but produce different signs and symptoms.
Pneumococcal pneumonia is the most common disease caused by pneumococcal infection. An estimated 400,000 hospitalizations from pneumococcal pneumonia occur in the United States annually.
Pneumococcal pneumonia can occur in combination with bacteremia and/or meningitis (invasive pneumococcal pneumonia), or it can occur alone (non-invasive pneumococcal pneumonia). Non-invasive pneumococcal pneumonia can be severe. Symptoms include abrupt onset of fever, shaking chills or rigors, chest pain, cough, shortness of breath, rapid breathing and heart rate, and weakness. The fatality rate is 5%–7% and may be much higher in older adults. Pneumococcal bacteremia occurs in about 25%–30% of patients with pneumococcal pneumonia.
About 4,000 cases of pneumococcal bacteremia without pneumonia occur each year in the United States. Bacteremia is the most common clinical presentation among children less than two years, accounting for up to 70% of invasive disease in this age group.
Pneumococci cause 50% of all cases of bacterial meningitis in the United States. There are an estimated 2,000 cases of pneumococcal meningitis each year. Symptoms and signs may include headache, tiredness, vomiting, irritability, fever, seizures, and coma. The case-fatality rate of pneumococcal meningitis is about 8% among children and 22% among adults. Permanent neurological damage is common among survivors.
Pneumococcal disease is a serious disease that causes much sickness and death. CDC estimates that more than 150,000 hospitalizations from pneumococcal disease occur annually in the U.S. An estimated 30,300 cases and 3,250 deaths from invasive pneumococcal diseases (IPD-bacteremia and -meningitis) occurred in the United States in 2019 (see www.cdc.gov/abcs/downloads/SPN_Surveillance_Report_2019.pdf.). Children younger than age two years and adults age 50 years and older) have the highest incidence of serious disease. Case-fatality rates are highest for pneumococcal meningitis and bacteremia, and the highest mortality occurs among older adults and patients who have underlying medical conditions. The overall case-fatality rate for pneumococcal bacteremia is about 20%. Among older adults, this rate may be as high as 60%.