The term bilateral is a synonym for double. Whether the disease is referred to as bilateral or as double pneumonia, the meaning is very simply the same: it is a case where the pneumonia affects both lungs of a patient. When the word "severe" is added to the diagnostic conversation, it is the worst of all possible pneumonia worlds: a very serious bacterial or viral infection, affecting not one but both lungs.
The minimal amount of documented research on severe bilateral pneumonia is a reflection of the fact that the disease is very rare in today's modern, medical age. Except for the poorest regions of the Third World, pneumonia is usually detected in one lung before it passes on to the second, and-or is treated and attacked long before it becomes "severe."
In the case of one 22-year-old patient, the cause of the disease was found to be even more remote. Rather than a straightforward bacterial or viral infection, she contracted the condition due to Cushing's Syndrome related to an adrenal carcinoma.
High-Risk Work Environments
Still, there is a group of laborers at high risk with regards to bilateral pneumonia: miners. Many individual and class-action court cases have been fought based on the unhealthy conditions of domestic and international mines, and the resulting contraction of all sorts of respiratory diseases, including bilateral pneumonia.
In the case of miners, there are all sorts of compounding factors. One study involved the analysis of organs dissected from African miners who died between 1996 and 2000. HIV, and many other complicating factors, were partly responsible for the break-down of their healthy lungs. The most common form of pneumonia found in more than half the sampled group was pneumocystis jirovecii. Another one-time trigger of severe bilateral pneumonia, asbestos, has thankfully been largely excised from the modern work and home environments.