Through the evolutionary history of being used by the wasps, these viruses apparently have become so modified, they appear unlike any other known viruses today.

The virus developed the three expected resistance mutations and became inactive.

The change was nonetheless interpreted by some as indicating that the virus itself was becoming more deadly over time.

The virus was becoming an epidemic in southern Africa.

The viruses are also becoming more dangerous to computer users.

He noted that the virus is becoming more common among intravenous drug users.

But the virus had suddenly become much more deadly.

As if that were not intimidating enough, viruses and worms are becoming more dangerous.

Certain viruses have become more lethal in the past few years, and are even affecting people who are normally very healthy.

The virus became, he said mildly, "interpolated with economic and political concerns."