Infectious pneumonias are lung infections caused by various pathogens, including bacteria, viruses, and fungi. Common bacteria responsible for pneumonia include Streptococcus pneumoniae and Haemophilus influenzae. Symptoms often include cough, fever, chest pain, and difficulty breathing. Transmission typically occurs through respiratory droplets when an infected person coughs or sneezes. Risk factors include age, weakened immune systems, and chronic health conditions. Vaccines, such as the pneumococcal vaccine, can help prevent certain types of bacterial pneumonia, while antiviral medications may be used for viral infections.