Pneumonia is usually caused by infection with both viruses and bacteria. It is a lung infection (an inflammatory condition of lung) that makes us very sick.
Primarily it affects the microscopic air sacs called alveoli as the alveoli fill with pus and fluid, making the gas exchange difficult.
Often, it is preceded by influenza, commonly known as "the flu". Typical symptoms include a cough, chest pain, high fever, and difficulty breathing.
