The absence of symptoms in secondary tuberculosis may be due to the disease being in the latent stage or to the fact that mild symptoms have appeared, but have been ignored. 1. Some cases of secondary tuberculosis have a rapid onset, while others have a slow onset. Those with a slow onset have symptoms that appear later, so they may not have symptoms for a while. 2. Secondary tuberculosis is still in the latent stage, the inflammation has not spread and has not invaded other parts of the body, so there may be no symptoms. 3. The most typical symptom of secondary tuberculosis is blood in sputum. Some patients may have had symptoms before, but they are very mild and not obvious, so it may not be that there is no symptom at all, just that it has not attracted the patient’s attention. Even if there are no symptoms, it is recommended that secondary tuberculosis be treated as soon as possible.