All the strains of the virus are the same as his.

"After all, it almost certainly still has strains of the virus in storage,"

One strain of the virus, which brings a painful death within a week, might be carried through the air.

But they also seemed to be infected with weaker strains of the virus.

But doctors didn't anticipate another strain of the virus which has affected many children.

But, he added, there is no way to tell, by looking at the virus strain, whether it will be particularly virulent.

This finding suggests that they are different strains of the same virus or likely distinct species.

"This strain of the virus is even more robust than I'd imagined."

Even if the virus strains are the same specific variety, the antigenicity is very different.

These are very similar, as they are made to match the specific virus strain.