According to recent U.N. estimates, only 10 percent of the 15 million fishers are employed on large-scale fishing vessels.

CNN: Greenpeace: Industrial fishing fleet should be halved

Dr. Margaret Chan, the U.N. agency's director-general, said the decision to raise the alert on the 6-point scale indicated that all countries should "immediately" activate pandemic preparedness plans.

CNN: WHO raises pandemic alert to second-highest level