For the third time, the World Health Organization declined on Friday to declare the Ebola outbreak in the Democratic Republic of Congo a public health emergency, though the outbreak spread this week into neighboring Uganda and ranks as the second deadliest in history.

An expert panel advising the W.H.O. advised against it because the risk of the disease spreading beyond the region remained low and declaring an emergency could have backfired. Other countries might have reacted by stopping flights to the region, closing borders or restricting travel, steps that could have damaged Congo’s economy.

Dr. Preben Aavitsland, a Norwegian public health expert who served as the acting chairman of the emergency committee advising the W.H.O., said there was “not much to be gained but potentially a lot to lose.”

At the same time, the committee of 10 infectious disease experts said in a statement that it was “deeply disappointed” that donor nations have not given as much money as the W.H.O. and affected nations need to battle the outbreak.