MONROVIA, Liberia — Racing along cracked and bumpy roads here, Gordon Kamara shouted into his cellphone over the shrieking sirens of his ambulance. The phone had been ringing nonstop since 5 a.m.

“Not today! Not today!” Mr. Kamara, an ambulance nurse, yelled later in the day. “We are on the opposite side of town!”

The calls have all been the same in recent weeks: from friends, friends of friends, extended family, complete strangers. All of them have loved ones sick with Ebola and beg him to come quickly. Seven days a week, Mr. Kamara and his crew span Monrovia, Liberia’s capital, in a donated, old American ambulance — with California license plates still attached.

“It never stops,” said Mr. Kamara, getting another call the moment he hangs up.

The 15 or so ambulance teams bolting around the city have had many days of hard choices like this. Hundreds of new Ebola cases are reported each week in Monrovia, with many more never accounted for. And over the course of the epidemic, only a small percentage of them have ever made it to a hospital.

“We see it flow through the communities; first one, then many,” Mr. Kamara said. “The map is being painted red with the virus.”

To confront the spread of Ebola, some community groups have stepped in, motivated by altruism, desperation and, in some cases, political opportunism.

In some neighborhoods, teams of volunteers fan out to track victims and educate households on staving off the virus, though their pockets are so shallow that they often do not have enough supplies, like chlorine, to thwart the epidemic’s advance.

Mr. Kamara does not work for the government. He does not even have a dispatcher to tell him where to go, or which patients to pick up. Instead, his team is financed by an opposition member of Parliament, Saah H. Joseph, who imported two used American ambulances to Monrovia this year.