• Rhinoviruses
• Coronaviruses
• Influenza virus

• Paramyxovirus (like mumps)
• Most common cause of bronchiolitis and pneumonia in children under 2
• It inflames bronchioles and restricts air to alveoli

1.  Pneumococcal Pneumonia

• Streptococcus pneumoniae
• Called typical or lobar pneumonia
• Involves bronchi and alveoli
• High fever, chest pain, bloody sputum

2.  Mycoplasmal Pneumonia

• Mycoplasma pneumoniae
• No cell wall
• Walking or Atypical pneumonia
• Aerobic

• Inflammation of the lining of the pleural membranes
• Can occur as a result of pneumonia or tuberculosis
• Usually a viral pathogen
• Very painful, sharp stabbing pain accompanies inspiration

• Orthomyxoviridae
• Can cause endemic, epidemic, and pandemic influenza
• Fever, myalgia, headache, pharyngitis
• H spikes allow viral recognition to host and attachment
• N spikes help virus exit the infected host cell
• Viral strains based on H and N antigens

• Bordetella pertussis
• Gram-Negative coccobacillus
• Aerobic
• Attaches to and multiply in ciliated tracheal cells but don't invade deeper
• Many toxins: tracheal cytoxin damages ciliated cells, pertussis toxin causes systemic symptoms
• Cold symptoms, gasping for air
• Secondary complications can be CNS anoxia, secondary pneumonia
• Major cause of death worldwide

• Mycobacterium tuberculosis
• Gram-Positive bacillus
• Aerobic
• Waxy outer coat; grows slowly and in clumps
• Acquired by inhalation

• If infective dose is low, can fight it via activated macrophages
• If infective dose is high:

1. bacteria are ingested by alveolar macrophages and walled off in alveoli (tubercle)
2. Lesion becomes calcified
3. If defenses fail, tubercle breaks down and bacilli are released into respiratory, lymphatic, and cardiovascular systems

• Many species, spores inhaled regularly ; most harmless
• Aspergillus fumigatus can cause allergic bronchopulmonary aspergillosis or aspergillomas, fungal balls of entangled hyphae

• Inhale fungal spores of Histoplasma capsulatum
• Found in feces of starlings, pigeons, chickens, bats (soil with high nitrogen content)
• H. capsulatum is dimorphic; yeast like in tissue growth, filamentous in soil
• Resembles TB; lesions in lungs but spread via blood and lymphatics
• Usually asymptomatic