Is this the same H1N1 flu that killed 50 million people in 1918?

No. Even though the new flu virus has the H1 and N1 proteins on its outside, it’s a different strain.

A new study (published in the May 2009 issue of Journal of Virology) suggests that the devastating H1N1 flu that swept the world in 1918 was also able to infect pigs, but not kill them. The virus adapted to the pigs and resulted in the current lineage of the H1N1 swine influenza viruses.

So while there are some similarities, there are also important differences. In particular, the new virus is missing an amino acid that scientists think increases the number of virus particles in a person’s lungs and makes the disease more deadly. And it resembles other common flu strains closely enough that people may actually have some immunity. (Some scientists even think that this year’s flu vaccine, which contained a different strain of H1N1 influenza, could offer partial protection.)

So will getting sick now protect me later?

Possibly, but no public health officials are recommending deliberate exposure.