You have only one sneeze. Use it wisely.

Yes, it’s Stop Swine Flu, the video game.

The action starts with a schplouuush of green mucus hitting your screen, then switches to a street somewhere. Your avatar stands among pedestrians. The background noises are coughs, sneezes, noses being blown. Choose your moment, then tap the space bar to sneeze. Everyone hit by your spray turns green, then sneezes in turn, infecting others. How many are infected determines whether you go to the next level, which could be a train station, a factory floor or a nursery school.

Infecting a child is 5 points, an elderly person is 15.

“I sort of like it, but I think it’s really warped,” said an 8-year-old who noticed the game on Sunday when it reached the Top 10 on his favorite free children’s game site, www.miniclip.com.

Stop Swine Flu  which probably ought to be called Spread Swine Flu  is actually a new name for a game released this year as Sneeze, before the possibility of pandemic flu dominated the news. And Sneeze was created with the best of intentions: to subversively teach young people healthy habits. It was commissioned by the Wellcome Trust, the world’s second largest charity after the Bill & Melinda Gates Foundation.

“We did it to engage the older teen audience and teach them that where you sneeze matters,” said Daniel Glaser, the trust’s chief of special projects. “All the science is embedded in a contest that will look familiar to the YouTube generation.”