There are four levels of asthma severity classification
Mild Intermittent asthma (comes and goes)
--when your asthma is not well controlled, you have asthma symptoms twice a week or less, and you are bothered by symptoms at night twice a month or less.
Mild persistent asthma
--when your asthma is not well controlled, you have asthma symptoms more than twice a week, but no more than once in a single day. You are bothered by symptoms at night more than twice a month. You may have asthma attacks that affect your activity.
Moderate persistent asthma
--when your asthma is not well controlled, you have asthma symptoms every day, and you are bothered by nighttime symptoms more than once a week. Asthma attacks may affect your activity.
Severe persistent asthma
--when your asthma is not well controlled, you have symptoms throughout the day on most days, and you are bothered by nighttime symptoms often. In severe asthma, your physical activity is likely to be limited.
Anyone with asthma can have a severe attack - even those who have intermittent or mild persistent asthma.