“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.
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).
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.