Now, a century later, we have flu vaccines that have reduced the?severity?of epidemics.

These vaccines need to be updated every year because the virus changes and new?strains emerge.

What researchers fear is that a new strain of the virus will develop and cause another pandemic.

Once an?outbreak occurs, transmission of the disease will be even faster than before.

An unintended consequence of our improved transportation system will be the speed at which an epidemic can spread.

Experts predict that public health systems will be overwhelmed and unable to react quickly enough.

(A new strain of a virus is a mutated form of the virus.)

So the best?defense will be to prevent an?outbreak?from?occurring.

This will require global cooperation and the sharing of data.

It may also require changes in how humans?interact with animals.

Animals such as birds and pigs carry viruses that may?mutate into a?strain that can infect humans.

Such a new strain could lead to another pandemic well before a new vaccine could be developed.

Since diseases and epidemics don't stop at national boarders, this is a global issue requiring global action.

The threat of a global epidemic is another example of why we must learn to live together.

(An improved transportation system allows epidemics to spread more quickly.)

(A new strain of a virus is one that has mutated from the original.)