Double pneumonia, defined by Medicine Net as a pneumonia infection in at least one lung lobe in both the right and left lungs, is quite serious and potentially lethal. Any persistent respiratory illness should be evaluated by a doctor as soon as possible.
WebMD defines pneumonia as a serious bacterial or viral infection in the lungs, as opposed to the bronchial tubes. Pneumonia often develops after a person has had a cold, the flu or bronchitis, but it may occur on its own. Those with chronic diseases such as asthma, heart disease or cancer are more likely to catch pneumonia.
According to WebMD, the primary symptom of pneumonia is a vicious, often productive cough. Phlegm and mucus coughed up may be clear, green, rust-colored or flecked with blood. Fast breathing and shortness of breath is common, as the infection interferes with the body's ability to breathe. Other symptoms include fever, extreme chills, shaking, weakness and lethargy, nausea, diarrhea, vomiting and elevated heartbeat. Confusion can also result due to lack of oxygen.
If diagnosed by a doctor early, recovery from pneumonia can occur at home within two to three weeks, often while taking antibiotics or antiviral drugs. However, as WebMD points out, serious cases require hospitalization. In older patients the symptoms may vary or be suppressed, so vigilance is required to notice any changes in health.