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Bernice Dahn, Liberia's deputy health minister, has placed herself under a three-week quarantine because her office assistant died of Ebola, The Associated Press reports.

The World Health Organization recommends a 21-day isolation period for anyone who suspects that he or she has been exposed to Ebola, as officials say that is the maximum incubation period for the virus. Liberia has implemented those recommendations, so while Dahn said she was not experiencing any symptoms, she was still taking the precautions.

"Of course we made the rule, so I am home for 21 days," Dahn said. "I did it on my own. I told my office staff to stay at home for the 21 days. That's what we need to do."

Health workers treating patients in the West African countries affected by the Ebola outbreak are particularly susceptible to contracting the virus, which is spread by bodily fluid transmissions. WHO reports that more than 300 doctors and nurses in Guinea, Liberia and Sierra Leone have contracted the virus, and nearly half of the infected health workers have died.