Streptococcus pneumoniae is a type of bacteria that commonly causes infections in humans. It is known for leading to illnesses such as pneumonia, meningitis, and otitis media (ear infections). This bacterium is typically found in the upper respiratory tract and can spread through respiratory droplets when an infected person coughs or sneezes. In healthy individuals, Streptococcus pneumoniae may not cause any symptoms, but it can be dangerous for young children, the elderly, and those with weakened immune systems. Vaccines are available to help prevent infections caused by this bacterium, making them an important public health tool.