(CNN) -- The World Health Organization raised the swine flu alert to level five Wednesday indicating it fears a pandemic is imminent.

On Wednesday, the outbreak grew in terms of confirmed cases, people killed and countries with infections. 

Health officials are scrambling to get more information about the virus for which there is no vaccine.

"All countries should immediately activate their pandemic preparedness plans," said Dr. Margaret Chan, the World Health Organization`s director-general.

She added: "We do not have all the answers right now but we will get them."

Earlier, Dr. Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases, said: "It`s a virus that we`ve never seen before. There`s no background immunity in the population and it is spreading from human to human, all of which has the potential for a pandemic."