1.   In other mice in which colonies of normal human cells were grafted, the virus had little or no effect.

2.   The virus has a structure of relatedness that traces its roots further and further into the past.

3.   Viruses have a regular geometric shape.

4.   The virus has yet to make much headway in the wider community.

5.   Although the virus has yet to move north to Canada, the Canadian health authorities plan to catch it in the act if it does.

6.   Besides its predilection for crows, robins, chickens, hawks and other common bird species, West Nile virus has another feature that worries public health authorities.

7.   -- Medical researchers will discover that the HIV virus has nothing to do with AIDS.

8.   A virus actually has to be created and spread before they can build a defense against it.

9.   For example, no one knows why this virus had such unprecedented virulence.

10.   However, a reason for optimism is the general belief that a virus has to replicate to mutate and with a low level of replication chances for mutations drop.