WASHINGTON (AP) — President Barack Obama says the Ebola virus is controllable with standard public health measures and the U.S. is working with allies to send additional medical workers to West Africa.

The use of an experimental drug to treat American aid workers raises ethical questions about who should get any additional, limited supplies of a drug that’s never been tested in people. Obama says all the information isn’t in about whether the drug is helping.

In his words, “We’ve got to let the science guide us.”

Obama says this outbreak has spread more rapidly than previous ones in part because affected countries’ public health systems have been overwhelmed, but bolstering efforts to rapidly identify and isolate patients can work.

Obama spoke Wednesday at a news conference concluding a summit with African leaders.

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