Final answer:
Respiratory diseases can be caused by viruses, bacteria, and fungi. Viruses, such as the common cold and flu, are the most common cause of respiratory tract infections. Bacterial infections like tuberculosis and whooping cough are spread through respiratory droplets.
Step-by-step explanation:
Respiratory diseases can be caused by various pathogens, including viruses, bacteria, and fungi. Viruses are the most common cause of respiratory tract infections. For example, the common cold and flu are caused by viruses. These pathogens can be transmitted from person to person through coughing and sneezing. On the other hand, bacterial infections such as tuberculosis and whooping cough can also affect the respiratory system and are spread through respiratory droplets.