You may experience the sudden onset of one or more symptoms, such as:

Some children however, will present a sudden onset of symptoms, especially those with seizures.

Have sudden onset of high blood pressure, especially in a person older than age 50.

The pain may begin gradually or have a sudden onset.

There is a sudden onset of the disease at one to two years of age.

This would be expected with sudden onset of symptoms for example.

Of course to people who haven't heard its sudden onset before it sounds spontaneous.

Despite the sudden onset of the event, its impact lingers for 100,000 years.

The condition is usually characterized by a sudden onset of knee pain, worse at night.

Even after six years, the war's sudden onset was as real as the night before.