Pick the Flu


Influenza or "flu" is caused by a virus. The flu virus has only 8 genes, and two of them, abbreviated H and N are responsible for infecting us.

There are 16 different H genes and 9 different N genes. The flu virus has the clever ability to mix and match different combinations to come up with new viruses.

Different flu strains are named after the various combinations of the H and N genes.

  • Spanish flu (1917-1918) is called the H1N1 strain
  • Hong Kong flu (1968-1969) was caused by the H3N2 strain

When we make antibodies to the proteins that the H and N genes make, the antibodies protect us from being infected with the same strain of virus a second time.


Each year, health officials meet in early spring and decide what flu strain they think will cause the most infections in the coming fall and winter and make a vaccine against that strain.

Lets see if you can choose the right strain of virus to make a vaccine for and protect yourself from being infected this winter.

Be a World Health Organization (WHO) or a Center for Disease Control and Prevention (CDC) health official and predict which flu virus will be causing disease this winter.

Choose one of the 16 possible H genes:

Choose one of the 9 possible N genes:


You have predicted that H: and N: will be the virus that is going to be infecting us this winter. A flu vaccine against H: N: has been made and given to everyone.

Lets see if you have chosen the correct flu strain for the vaccine.

Click the button to see which flu strain will actually be infecting people this winter:

   H    N

imageCongratulations! You have predicted the correct flu strain, everyone is protected.

imageOh, no. You have guessed wrong. Many people will become sick because their vaccine was made to the wrong strain of the flu virus.