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.