Although pneumonia can be caused by a variety of viruses, bacteria and fungi, S. pneumoniae is the most dangerous. The Centers for Disease Control and Prevention (CDC) estimate that Streptococcus pneumoniae is responsible for 500,000 cases of pneumonia and 40,000 deaths in the US each year, more deaths than for any other vaccine-preventable bacterial infection. In addition, the disease also causes 3,000 cases of meningitis (infection of the lining of the brain and spinal cord), 50,000 cases of bacteremia (bacteria in the blood), and 7 million cases of otitis media (inner ear infection) in the US.

It is thought that at any given time, 70% of healthy people have pneumococcus in the mucous of their noses and throats. Scientists don't know what causes pneumococcus to suddenly invade lungs to cause disease. Pneumococcal pneumonia can begin suddenly with a severe chill and shaking usually followed by high fever, cough, shortness of breath, rapid breathing and chest pains. Other symptoms may include nausea, vomiting, headache, fatigue, and muscle aches. The diagnosis of pneumonia involves symptoms, physical examination, lab tests, and chest x-rays. The presence of S. pneumoniae in blood, saliva, or lung fluid helps to differentiate pneumococcal pneumonia from other causes. Early diagnosis and appropriate antibiotic therapy helps to reduce the severity of the disease. Bacteria continually develop resistance to antibiotics which can affect the choice of therapy. Currently quinolone antibiotics are often the drugs of choice for community-acquired pneumonia. A serious complication associated with pnemococcal pneumonia involves the presence of bacteria in the blood, known as bacteremia, which can cause heart problems.

Vaccination is an important method for the prevention of pneumococcal pneumonia. The CDC National Immunization Program (NIP) recommends immunization with pneumococcal polysaccharide vaccine for anyone 65 years or older, people aged 2 to 64 with serious chronic illness such as diabetes, heart disease, chronic obstructive pulmonary disease, or liver disease, people with compromised immune function such as those with HIV, leukemia, kidney disease, undergoing cancer treatment, long term corticosteroid therapy, or with a damaged or no spleen. Asthma has not been associated with increased risk of pneumonia unless asthma is in combination with chronic bronchitis, COPD, or long-term corticosteroid therapy. The NIP also recommends children under 23 months of age be immunized with the new conjugated vaccine. It is estimated that half of the deaths caused by pneumococcal pneumonia could be prevented by vaccination. Antibodies to vaccine remain elevated for at least 5 years in healthy adults. Side effects to the vaccine are usually limited to mild, local reactions. Other prevention methods include avoiding contact with infected persons and washing hands often with soap and water or disinfectant gels.

References: http://www.cdc.gov/mmwr/PDF/rr/rr4608.pdf, http://www3.niaid.nih.gov/healthscience/healthtopics/pneumonia/default.htm

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