Haiti is still reeling from Category 4 Hurricane Matthew, which killed hundreds of people and left thousands more without their homes. (Victoria Walker,Joshua Partlow/The Washington Post)

A week after Hurricane Matthew leveled swaths of western Haiti, the relief effort is finally gaining steam, with the flow of food and medicine increasing to cities that will serve as hubs for desperate outlying villages, aid workers and diplomats say.

The storm that struck on Oct. 3 killed hundreds of people and forced thousands from their homes, setting off the worst humanitarian crisis in this impoverished country since the devastating earthquake six years ago. Winds tore buildings apart, and flooding has contaminated water supplies and helped spur a new outbreak of cholera along the coast, with at least 200 cases reported, according to the United Nations.

“I’ve seen it from the air, and it looks catastrophic,” U.S. Ambassador Peter F. Mulrean said in an interview Tuesday. “I’ve seen it from the ground, and it is heartbreaking.”

In some areas, residents have erected roadblocks with logs and brush to stop aid trucks so that they can ransack the supplies. Increasingly desperate survivors are pleading for food, water and shelter.

“There have been worrying instances of looting of international aid and assistance on their way to most-affected communities,” said Ariane Quentier, spokeswoman for the U.N. Stabilization Mission in Haiti. “In more general terms, there are tensions mounting within communities awaiting help, which is also a worrying development.”

People wash clothes on a beach near ruined houses on Oct. 10, 2016, a week after Hurricane Matthew hit Jeremie, Haiti. (Carlos Garcia Rawlins/Reuters)

Haiti’s national civil protection agency has increased the death toll nationwide from the hurricane to 473, but that seems likely to grow, and some estimates put it at more than 1,000. Some 175,000 people are living in shelters.

The World Health Organization announced Tuesday that it was sending 1 million doses of cholera vaccine to Haiti. It said about one-quarter of the health-care facilities in southern Haiti had been destroyed or seriously damaged. Cholera can be deadly and is transmitted through contaminated water or food.

American officials say the priority for relief remains saving lives: providing food and clean drinking water by truck, boat or helicopter to many communities that remain hard to reach.

A U.S. disaster response team of more than 50 people has bivouacked in the atrium of the U.S. Embassy here, while the American military is working out of the airport, with about 425 affiliated personnel, moving relief supplies by helicopter.

A cargo flight of U.S. government relief supplies, the fifth so far, was scheduled to arrive Tuesday and was to include hygiene items, cooking kits and tarpaulins for homes that lost their roofs. The U.S. government is working with charities and aid groups to hasten the distribution to remote villages.

The Haitian government, operating with an interim president, has seemed largely absent from many shattered coastal towns. Aid workers and diplomats, however, say the government’s civil protection agency has been actively putting together the strategy for the hurricane response while relying on foreign donors to bring in the supplies and carry out the plan.

Haiti is in the midst of a long-running political crisis. Last year’s first round of the presidential election was engulfed in accusations of fraud, and the second round was repeatedly delayed. An interim government, led by Jocelerme Privert, remains in charge, although his mandate expired in June. A presidential election scheduled for this past Sunday was postponed indefinitely because of the hurricane.

Robert Perito, a Haiti expert and adjunct professor at George Mason University’s School of Policy and Government, said the fact that Haiti’s government was organizing an election was distracting officials from the immediate disaster relief.

The “government is simply not present in many areas” and is “always slow to respond when it reacts at all,” he said. “Haitians are prickly about their sovereignty, but this is an interim government with little capacity, so incompetence is probably a factor.”

Mulrean, the U.S. ambassador, said he has met or spoken with Privert almost every day and has toured the hurricane-damaged zones with him twice. Emergency operations centers in the capital and around the country, set up after the earthquake, are functioning well, and have embedded U.S. staff, he said.

The government is “interim, but it’s in place, and they took their responsibility very seriously,” Mulrean said. “We’ve got a government that wants to be out front. That we want to be out front. Obviously they need a lot of support. And we and others are prepared to do that.”

The provisional electoral council has met in recent days with the government and foreign ambassadors to discuss the timing for an election, but no date has been proposed.

“Everyone agrees that the elections need to move forward and need to be completed and that having a newly elected president in place will allow the government to deal [better] with the longer-term issues than having a provisional government in place,” the ambassador said. He added that it was important to find “the balance between the political imperative to hold the elections as quickly as possible and what is technically feasible to run credible elections.”

Among the main difficulties for the relief effort so far has been the inaccessibility of the villages battered by the storm. It struck the western edge of the Tiburon Peninsula, cutting off an already remote part of the country, a region where one paved road is often the only way to reach towns. Many of those roads were made impassable by fallen trees and washed-out bridges.

U.S. officials said that communications had collapsed in the hurricane but were slowly coming back.

Two cities, Jeremie and Les Cayes, have become hubs for shipments of food and other supplies that are to be distributed to smaller coastal villages.

Beyond the immediate survival needs, Haiti faces a mass rebuilding effort, as thousands of homes and other buildings were damaged or destroyed. The peninsula is an important agricultural area, producing rice, fruit, cassava and other crops, and much farmland was damaged.

“In some parts of Haiti you have 90 percent of homes destroyed, plus people losing all their crops,” said John Hasse, national director in Haiti for the aid group World Vision. “For them, it’s not just about getting immediate relief supplies; it’s more like: What happens next week? What happens next month?”

Filipov reported from Washington.