Too many people.
Nasal congestion is the condition where the tissues in the nose, including the sinuses, are irritated and swollen. The irritation causes the production of mucous, and the swelling causes difficulty breathing.
Yes, it is.
Too many cars and too many people..until butt comes...
Rotavirus
Nasal congestion can be caused by a common cold. It can also be caused by seasonal allergies and from dust, dirt, etc.
Japanese urban areas are good settlements since they are fully developed. The infrastructure is in good shape but there is also the risk of congestion.
bad
vitamin c
sinusitis
It would most likely be caused by allergies.
Congestion in the lungs or (more likely) bronchial tubes.
It can be anything from a cold, allergies to upper respiratory infection.