Streptococcus pneumoniae pneumonia: This is the most common cause of community-acquired pneumonia (CAP), presenting with symptoms such as high fever, chills, cough, and difficulty breathing. It is more typical in presentation and often responds well to beta-lactam antibiotics.

Influenza pneumonia: Especially during flu season, influenza can cause pneumonia, either directly or by complicating a primary viral infection with a secondary bacterial infection. Symptoms can include fever, cough, sore throat, and muscle aches.
Mycoplasma pneumoniae pneumonia: This atypical pneumonia is common in younger adults and presents with symptoms such as cough, fever, and headache. It is known for its extrapulmonary manifestations and often has a more gradual onset.
Chlamydophila pneumoniae pneumonia: Another cause of atypical pneumonia, it presents similarly to Mycoplasma pneumoniae and is known for causing outbreaks in closed environments like schools and military barracks.
Legionella pneumonia: Caused by Legionella pneumophila, this atypical pneumonia can present with high fever, cough, and gastrointestinal symptoms. It is more severe and can be associated with outbreaks related to contaminated water sources.

Pneumocystis jirovecii pneumonia (PCP): Especially in immunocompromised patients, such as those with HIV/AIDS, PCP can present with non-specific symptoms like dry cough and progressive dyspnea. It is crucial to consider in patients with risk factors due to its high mortality if untreated.
Tuberculosis (TB): While less common in some regions, TB can present with chronic cough, weight loss, and night sweats. It is critical to diagnose due to its public health implications and the need for specific treatment.
Influenza A (H1N1) or other viral pneumonias: In certain contexts, such as during a pandemic, these can be significant and deadly if not recognized and managed appropriately.
Severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS): Although rare, these viral pneumonias have high mortality rates and require immediate isolation and treatment.

Q fever: Caused by Coxiella burnetii, it can present with atypical pneumonia symptoms and is usually associated with exposure to animals or contaminated products.
Psittacosis: Caused by Chlamydophila psittaci, this atypical pneumonia is associated with exposure to birds, particularly parrots and pigeons.
Hantavirus pulmonary syndrome: A rare but severe condition caused by viruses transmitted through contact with rodents or their droppings.
Fungal pneumonias: Such as those caused by Histoplasma, Cryptococcus, or Aspergillus, which are more common in immunocompromised individuals or those with specific exposures (e.g., bird droppings for Histoplasma).