Wednesday, the Chinese Academy of Sciences said the H7N9 virus probably came from migratory birds from East Asia that mixed with domestic fowl in China's Yangtze River delta region around Shanghai.

CNN: WHO reports 5 new bird flu cases in China; total now 49

The contaminated ships have since been disinfected but with only mixed success, perhaps because a sick passenger (or one who is incubating the virus) can board and infect others.

FORBES: Magazine Article