It may also explain cases in which virus carriers did not form antibodies for a year or more.

"As a technical matter, checking for virus carriers may be very difficult."

Each case of paralysis implies that many more virus carriers are nearby.

Other experimental drugs may soon be available for testing among healthy virus carriers.

Other drugs are also being studied in healthy virus carriers.

Some state officials and other medical experts have expressed concern about the inability to inform patients if they are found to be virus carriers.

Other recent studies have found that some virus carriers do not form antibodies for many months or even years.

The virus carriers had been slow to travel on Lalonde.

And so it was floppies that were virus carriers back then.

Only about half the patients have chosen to be tested to see if they are virus carriers.