Sub-Saharan Africa, where the virus may have originated, is the hardest hit.

They must think the virus had originated in the school, or that the school was a major source of carriers.

The virus originated 50-150 years ago and has undergone a recent population expansion.

You'd better check Badri's contacts back four to six days, as well, in case the virus did originate with him.

My job is to try to find out where the virus originated.

It is not clear that all small viruses have originated from more complex viruses by means of genome size reduction.

But they said that they did not uncover enough data to say whether the virus originated in birds, pigs or other animals.

Guangdong is where health experts believe the virus originated.

This supports the theory that the virus originated in Israel.

Officials were immediately concerned about where the virus originated and where it might have spread.