Pneumococcal pneumonia: This is a common cause of effusion related to infection, particularly in the context of bacterial pneumonia. The presence of Streptococcus pneumoniae can lead to parapneumonic effusion, which is a collection of fluid in the pleural space associated with pneumonia.

Staphylococcal pneumonia: Staphylococcus aureus is another common pathogen that can cause pneumonia and subsequent effusion. It's known for its ability to cause severe infections, including those leading to empyema, which is a collection of pus in the pleural space.
Klebsiella pneumonia: This is a type of bacterial pneumonia that can lead to severe infections, including the formation of effusions. It's more common in certain populations, such as the elderly or those with underlying health conditions.
Tuberculous pleurisy: In areas where tuberculosis (TB) is prevalent, tuberculous pleurisy is a significant consideration for effusions related to infection. TB can cause a chronic infection of the pleura, leading to effusion.

Empyema: This condition, characterized by the collection of pus in the pleural space, is a medical emergency. It requires prompt diagnosis and treatment to prevent serious complications, including sepsis and death.
Lung abscess: A lung abscess can lead to the formation of an effusion, especially if the abscess ruptures into the pleural space. This condition can be life-threatening if not properly managed.
Fungal infections: In immunocompromised patients, fungal infections such as aspergillosis or cryptococcosis can cause effusions. These infections can be particularly dangerous and require early diagnosis and treatment.

Actinomycosis: This is a rare bacterial infection that can cause a variety of symptoms, including the formation of effusions. It's often associated with oral or gastrointestinal procedures.
Nocardiosis: Nocardia species can cause infections in the lungs, which may lead to effusions. This is more common in immunocompromised individuals.
Parasitic infections: Certain parasites, such as those causing amebiasis or echinococcosis, can infect the lungs and lead to effusions. These are rare in many parts of the world but should be considered in endemic areas or in patients with a history of travel to such areas.