killed at east 50 million people, some say as many as 100 million people,

but certainly at least 50 million people.

And that makes it the deadliest

single event in all recorded human history.

So it was a big deal, and if something like that

ever came back again, today, something just as deadly,

in today's population, which is much bigger,

as many as 400 million people could die."

The exact origins of the 1918 pandemic remain a mystery.

However, thanks to the work of scientists at NIAID and elsewhere,

we now know more about where the "Mother of All Pandemics" came from.

NIAID's Dr. David Morens explains.

Dr. Morens: "We know that in 1918, that virus was a brand-new virus

that had not been in people before. It was a bird virus; it came out of birds

and somehow, either directly or indirectly

got from birds into people.

But then, it didn't go away.

It kept mutating and evolving in people, and for decades,

it kept coming back in a different mutated form every year

until 1957, when it pulled another genetic trick

and was able to capture additional bird virus genes,

bird influenza virus genes, to make it so different that it resulted in another pandemic.

A similar thing happened in 1968, and a similar thing again in 2009.

So what that means is all these viruses that have been circulating

ever since 1918 are, in one way or another,

descendants of the 1918 virus."

Like in 1918, the next pandemic

could also come from an entirely new virus.

Dr. Morens: "The body parts of the viruses are out there in nature, in wild birds,

that can form together to form other viruses that are as deadly,

at least in theory, as deadly as the 1918 virus.

So this could happen again."

Currently, the best way to protect yourself from influenza

is to get a seasonal flu shot.

But even seasonal influenza evolves

and mutates from year to year, making the vaccine less effective.

What if we had a vaccine that could protect against

all kinds of influenza, both seasonal and pandemic?

In addition to his work on the 1918 virus,

NIAID's Dr. Jeffery Taubenberger

has researched potential universal vaccines.

Dr. Taubenberger: "And so the goal for this would be to develop a so-called

universal vaccine, and this could mean

different things to different people.

A more modest goal might be a vaccine that would give you protection, say,

for five or ten years against seasonal flu, so that you wouldn't

need the vaccine every year.

A broader goal would be a vaccine that could

prevent new pandemics from occurring.

Right now we can only react when a pandemic occurs,

and make a vaccine after it's already started circulating,

which is really too late.

So the goal would be, could you make a vaccine that could help

provide at least some protective immunity against

any kind of strain."

There are many different kinds of experimental universal flu vaccines,

which are designed to work in different ways.

Though some human trials have already begun,

even the most advanced experimental vaccines

are still years away from being publicly available.

Dr. Taubenberger: "I think that all these experiments will help

all of us, as a community, work to develop

new generations of vaccines.

But I feel confident that with

the amount of effort that's going on,

especially funded by the Institute,

that we will be able to make progress in this regard,

and make better influenza vaccines in the near future."