UNITED NATIONS — Nineteen thousand doctors and nurses will soon be needed to make a dent in West Africa’s Ebola outbreak, but the world has yet to send more than a small fraction of them, the United Nations says. Of the 1,000 vehicles needed to help the effort, only 69 have arrived. Of the 500 burial teams needed to ensure that infected corpses do not spread the disease, only 50 are now on the ground — and there is no clarity on who will pay them.

In the breach, Ebola is fast washing away the small gains made over the last decade in war-scarred parts of West Africa, as schools shut down, immunization campaigns are suspended and a food crisis looms as farmers abandon their fields.

Donors had spent millions of dollars in an effort to strengthen the public health systems of Guinea, Liberia and Sierra Leone long before the three countries became the center of the Ebola outbreak. Aid agencies of the United Nations have been active there for decades, with projects to train health workers, improve child mortality rates and get more children into school. United Nations peacekeepers helped shore up Sierra Leone for 20 years, since the end of its crippling war; Liberia had some 5,000 peacekeepers when the outbreak began this year.

Now, a virus that doctors have controlled elsewhere has ballooned in West Africa, unraveling many of the gains made in these countries in recent years and potentially threatening the hard-won stability of this tinderbox part of the world.