Even today, it is the sixth leading cause of death. It is still the number one cause of death from infection. It poses a particular threat to certain high-risk groups . Who gets such as the elderly and people with impaired immune systems. The two most common causes of pneumonia in older adults are bacteria and viruses .
Bacterial pneumonia is very serious.
Its most common form is Streptococcus pneumoniae , also known as pneumococcus . Although many other kinds of bacteria can cause pneumonia, pneumococcus is the only kind of pneumonia for which we have a vaccine . Pneumococcus bacteria can grow quickly and cause severe damage. The infection quickly spreads throughout the body. Half of all pneumonias are caused by viruses.