The World Health Organization said today that it is struggling to contain an unprecedented outbreak of the Ebola virus on the continent of Africa.

The contagious and deadly disease is spreading, in part because of trade, across the borders of three countries: Liberia, Guinea and Sierra Leone, health officials said.

In the outbreak zone, though, a new fear was growing: that some frightened patients are staying away from hospitals and sheltering at home or in churches, further spreading the disease.

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Liberian President Ellen Johnson Sirleaf today joined Sierra Leone in issuing a warning about hiding patients.

"Anyone found or reported to be holding suspected Ebola cases in homes or prayer houses can be prosecuted under the law of Liberia," Sirleaf said today during an interview.

Since March, the outbreak has killed at least 390 of the more than 600 people it has infected in the three countries, according to WHO.

There is no known cure for Ebola. In this outbreak - the largest for the Ebola virus - 62 percent of infected people have died.

Ebola spreads by close contact with the bodily fluids of infected people.

The virus is characterized by a sudden fever, intense weakness, vomiting, diarrhea and impaired kidney and liver function. In severe cases, it can cause internal bleeding.

The Associated Press contributed to this story.