Early symptoms of pneumonia often resemble a severe cold or flu, typically starting with a sharp or stabbing chest pain that worsens when breathing deeply or coughing, alongside a cough that produces green, yellow, or bloody mucus. As the infection takes hold, individuals frequently experience a high fever with shaking chills, shortness of breath or rapid shallow breathing, severe fatigue, and a loss of appetite. In older adults, these initial signs may present subtly as sudden confusion or a lower-than-normal body temperature instead of a fever.