“The flu,” more properly known as seasonal influenza, is a common contagious infection. The flu affects the nose, throat, and lungs. It is spread through droplets that have come from someone who has the flu through their cough or sneeze.
Coronavirus (including COVID-19)
Coronaviruses are a large family of viruses. They can cause diseases ranging from the common cold to more severe diseases such as Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS-CoV). Some transmit easily from person to person while others do not. COVID-19 (2019-nCov) is a respiratory infection that originated in Wuhan, China.
RSV or Respiratory Syncytial Virus is a common cause of respiratory illness most often affecting infants, young children and older adults although anyone can get sick with this respiratory virus. Most children are exposed to RSV and have been exposed at least once by the age of 2. Children especially young babies and older adults may experience cold like symptoms and bronchiolitis. More info on RSV can be found here on the Ontario Government site Respiratory Syncytial Virus | ontario.ca
Tuberculosis (often called TB) is a bacterial infectious disease that usually attacks the lungs, but can attack almost any part of the body. TB can be an active disease (infectious) or latent infection (not infectious).