Is bronchiolitis curable in adults and is it lifethreatening?

Yes, no. In adults, bronchiolitis usually is a mild disease. Goes away on its own and rarely threatens an adult's life. In the elderly and those who may be immunocompromised it may pose more serious threats.
Depends . It depends somewhat on the basic health of the patient. In most, i classify this midway between a cold and pneumonia in its effect on someones health & activities.Most respond well to proper management but often remain symptomatic with some cough for weeks.