The first outbreak of Ebola in West Africa has quickly grown to be the most severe in history, with more than 1,200 infected and 673 dead as of July this year. One Liberian doctor has died and two Americans have been infected in the course of treating patients.

The disease has spread quickly since the beginning of the current outbreak in February and is now three times larger than the last major outbreak in Uganda in 2000.

Liberia, Sierra Leone, and Guinea all have confirmed cases. For the first time, the disease was discovered to be spreading via air travel when a Liberian man became ill on a plane flying to Nigeria, Africa’s most populous country. Liberia has closed all but its main border crossings to limit transmission and Nigeria has put its entry points on red alert.

Ebola disease is caused by an extremely contagious virus with a high mortality rate that has varied between 50 and 90 percent in major outbreaks. The initial symptoms of the disease are similar to the flu and malaria potentially followed by vomiting, diarrhea, and bleeding, all of which can transmit the disease. There is no vaccine or specific treatment, but treating the disease’s effects, like dehydration, can reduce mortality.

The first outbreak of Ebola was in 1976, yet there are many facts about it that are unknown. Researchers have found the disease in a variety of wild animals but its natural maintenance host (the population from which new cross-species infections arise) is unknown, though fruit bats are suspected. The disease can infect gorillas, chimpanzees, dogs and pigs and can be readily transmitted between species.

It is unknown how the American doctor, Kent Brantly, and his colleague, Nancy Writebol, became infected while working for the aid group Samaritan’s Purse. Brantly was working with patients and Writebol was assisting doctors to remove their protective gear, which includes spraying them down with a chlorine solution. Both appear to have followed the procedures recommended by the Center for Disease Control and World Health Organization.

Ebola is primarily a rural disease, where food gathered from hunting exposes people to infected animals and lack of clean water spreads infection. The isolated conditions in rural West Africa limit the numbers affected, but if the disease spread to one of Africa’s large cities like Lagos, Nigeria, it could quickly overwhelm limited health care infrastructure.

The affected areas are some of the poorest in the world, with Liberia, Guinea and Sierra Leone ranked 13th, 9th, and 5th least developed countries in the world according to the United Nations.

Ibrahima Touré, the director of Plan Guinea, explained the effect this has in an interview with Africa Guinee: “The poor living conditions and lack of water and sanitation in most parts of Conakry [Guinea’s capital] poses a serious risk that this epidemic will become a crisis. People don’t think to wash their hands when they don’t have water to drink.”

Efforts to contain the outbreak are hampered by insufficient resources, public distrust of the government, and cultural practices like bathing the deceased before burial.

Angry locals have attacked health care workers out of deep distrust of the government. Samaritan’s Purse suspended outreach efforts in Lofa, Liberia after a crowd set up a roadblock and attacked health care workers who had come to collect a man suspected to be dying of Ebola.

In Sierra Leone, a woman was removed from a treatment center by her family and taken to a traditional healer. After the police retrieved her she died on the way to the hospital.

Last Friday, thousands of people surrounded the main treatment in center in Kenema, Sierra Leone, threatening to burn it down and remove the patients. Police dispersed the crowd with tear gas and shot a 9-year-old in the leg.

This opposition to medical treatment has its roots in the desperately poor living conditions and political instability of the area. Guinea last had a military coup in 2008 and its 2013 elections saw mass protests, with nine protesters killed and 220 wounded. Civil war in Sierra Leone ended in 2002 with 50,000 dead and many refugees fleeing to Guinea and Liberia. Liberia’s civil war ended in 2003 with new elections in 2005.

Under conditions of political instability and mass poverty, diseases like Ebola can reach epidemic proportions.