FREETOWN, Sierra Leone — The Ebola outbreak in Sierra Leone, which has been surging in recent weeks, may have reached its peak and could be on the verge of slowing down, Sierra Leone’s information minister said Wednesday.

But in a reminder of how serious the situation is in Sierra Leone, a ninth doctor became infected Wednesday and the World Health Organization said the country accounted for more than half of the new cases in the hardest-hit countries in the past week. By contrast, infections appear to be either stabilizing or declining in Guinea and Liberia, where vigorous campaigning for a Senate election this week suggests the disease might be loosening its grip.

In all, 15,935 people have been sickened with Ebola in West Africa and other places it has occasionally popped up. Of those, 5,689 have died. The case total includes 600 new cases in Guinea, Liberia and Sierra Leone in just the past week, according to the WHO.

The disease is transmitted through contact with bodily fluids of the sick, putting health workers at particular risk. Dr. Songo Mbriwa, a top military doctor who was working at a treatment center in the capital, tested positive for Ebola on Wednesday, according to Abass Kamara, a Health Ministry spokesman.

Nearly 600 health workers have become infected in the West African outbreak.

Still, Alpha Kanu, Sierra Leone’s minister of information, told journalists in an online press conference that with the imminent completion of two British-built treatment centers, the worst could be over for the country.