"This could trigger an epidemic, exposing the public at large to viruses known and unknown."

During the race, many of the team's riders and staff contracted an unknown virus.

Jenny reveals that she is suffering from an unknown virus.

But she suddenly died of "an unknown virus," the doctor said, which was why the coffin had to be sealed.

One such disease thought to be caused by an unknown virus is multiple sclerosis.

At the same time, cases of an new, unknown virus have been reported across the country.

The then unknown virus killed 32 people in just a few weeks, and sickened many others.

This can catch unknown viruses before they are included in the database.

Any person who has had this kind of xenografting should assume that they might have some unknown viruses.

But so far as I know, it is the only thing with which to fight an unknown virus.