The West Africa Ebola outbreak has claimed more than 670 lives so far, spreading into four countries. 

Its forest fire-like, rapidly-spreading nature, according to Stephan Monroe, deputy director of the C.D.C.'s National Center for Emerging and Zoonotic Infectious Diseases, makes it a relentless virus. And, like forest fires, the outbreak can be "reseeded," sparking onto a new patient and ravaging a new region, as long as more victims are available for contact.

And despite international efforts, the fire's been hard to put out. Susan Rice, President Obama's national security adviser, told Reuters the epidemic is "very worrying." In the meantime, she said, the U.S. will remain "very much present and active in trying to help the countries of the region and the international authorities like the World Health Organization address and contain this threat." 

Ebola has no treatment, no vaccine, and a fatality rate of up to 90 percent. Since its discovery in 1976, it has claimed more than 2,000 deaths out of its reported 3,140 cases, with the current version of the virus originally found in Zaire (now Democratic Republic of Congo).

"The response to this outbreak will be more of a marathon than a sprint," Monroe said.

We've traced coverage of the outbreak, and tracked its progress in the timeline below, as reported by the C.D.C. and the W.H.O.:

January 2014: Believed to be the month of origin of this outbreak, when the virus infected its first host and incubated.

February 2014: First cases of Ebola are reported in Guinea.

March 25, 2014: After suspected cases arise throughout its rural districts of Guekedou, Macenta, Nzerekore, and Kissidougou, the government of Guinea officially reports an outbreak of Ebola. Suspected cases are also reported in Liberia and Sierra Leone. Guinea enlists Doctors without Borders to establish Ebola treatment centers throughout the affected regions.

March 27, 2014: The virus reaches Guinea's capital of Conakry, the most populated—the city is home to 2 million people—site the outbreak has affected so far. The Bernhard-Nocht Institute of Tropical Medicine in Hamburg, Germany, and the Institut Pasteur in Dakar, Senegal, join the efforts of Institut Pasteur in Lyon, France, testing samples. Researchers confirm the virus is a strain of Ebola that had originally been discovered in Zaire (now Democratic Republic of Congo) in 1976.

March 29, 2014: The virus is confirmed to have reached Liberia.

March 31, 2014: More international organizations arrive in the region: The International Red Cross, Pentecostal Mission Unlimited, and Samaritan's Purse set up to spread awareness campaigns and distribute protective equipment. The W.H.O. leads the international response, and the C.D.C. sends a five-person team to help.

April 1, 2014: Guinea reports its first case of Ebola in the Djingaraye district, much farther north compared to the previously reported districts, indicating a new outbreak origin point.

April 7, 2014: The number of fatalities crosses 100 people, with 95 deaths in Guinea, and 7 in Liberia. Some of the cases include infected health workers.

April 30, 2014: The number of fatalities crosses 150 people, with 146 deaths in Guinea (16 of those being health care workers), and 9 deaths in Liberia. 

May 27, 2014: The number of fatalities reaches 200 people, with 186 deaths in Guinea, 9 in Liberia, and 5 in Sierra Leone—the first deaths reported in the country. The WHO and CDC confirm that the country's Kailahun district is the outbreak's hot spot, while laboratory testing begins in the city of Kenema.

May 28, 2014: For the first time, cases are reported from the counties of Boffa, Boke, and Dubreka in western Guinea, covering a new region of the country.

June 2, 2014: The first suspect case is reported in Liberia since April 9, and investigations begin to contain yet another outbreak point. The stretch of time between the reports in Liberia exceeded the 21 days for Ebola to incubate.

June 18, 2014: The number of fatalities crosses 300 people, with 264 deaths in Guinea, 24 in Liberia, and 49 in Sierra Leone.

July 8, 2014: The number of fatalities crosses 500 people, with 307 deaths in Guinea, 84 in Liberia, and 127 in Sierra Leone. 

July 18, 2014: The number of suspected cases crosses 1000, with 1048 people reached.

July 22, 2014: A Liberian official dies after landing in Lagos, Nigeria, the most populous city so far, with 21 million inhabitants. The death initiates a series of red alert responses from the country (now the fourth African country to include a case of Ebola), which increases surveillance at all ports of entry. Follow-up work begins in Togo, where the official's plane had also landed on its way to Nigeria.

July 23, 2014: The number of fatalities reaches 672 people, with 319 deaths in Guinea, 129 deaths in Liberia, and 224 deaths in Sierra Leone. In Sierra Leone, the leading doctor fighting the outbreak is reported to have been infected as well, after having treated more than 100 victims in the country.

July 25, 2014: Street protests occur in Kenema, Sierra Leone, resulting in police firing tear gas into the crowds that threatened the city's hospital. The protestors had planned to burn down the hospital and eradicate the virus—an approach that would not at all have prevented further outbreaks. Instead, the W.H.O. reports Guinea experiencing a surge in cases indicates further undetected chains of transmission.

July 26, 2014: The first death occurs in Sierra Leone's capital city of Freetown, and a leading doctor in Liberia succumbs to the virus.

July 27, 2014: The first Americans are infected in the outbreak. Both are health workers.

July 28, 2014: Nigeria suspends flights to Liberia and Sierra Leone for its largest air carrier, Arik Air. 

July 29, 2014: Nigeria's Asky Air follows Arik and suspends flights to Liberia and Sierra Leone. The airline will screen passengers flying out of Guinea. Meanwhile, Liberia has suspended all soccer-related activities, as sweat is a bodily fluid that could allow for Ebola transmission. And according to the BBC, Dr. Sheik Umar Khan, the leading Ebola doctor in Sierra Leone who contracted the virus on July 23rd, has died:

The New York Times also reports that Liberia has announced the closing of all schools. The country's nonessential government workers will go on compulsory leave for 30 days, and more security will carry out an action plan to fight the outbreak.

July 30, 2014: Peace Corps temporarily pulls 340 volunteers from Liberia, Sierra Leone, and Guinea, after two American Peace Corps volunteers were found to have been exposed to the disease. 

Later that day, Sierra Leone, more than two months after the first cases appeared in the country, declares a health emergency over the outbreak. President Ernest Bai Koroma calls for the deployment of security forces to quarantine epicenters of infection, as well as the cancellation of his planned visit to the U.S. From the New York Times:

Public meetings will be restricted, houses will be searched for infected people, Parliament will be recalled and top officials will be obliged to cancel all but essential overseas travel.

'These measures will initially be implemented for a period of 60 to 90 days,' Mr. Koroma said, 'and subsequent measures will be announced as and when necessary.'

The total number of cases, according to the WHO, stands at 1,323 people, with 729 deaths. 

August 4, 2014: Nigerian authorities confirm a second case of Ebola in the country, prompting a quarantine of eight others who may have come into contact with Patrick Sawyer, the Liberian-American man who died after landing in the Lagos airport.

Meanwhile, Mount Sinai Hospital in New York City said it is testing a patient who traveled from a West African country for Ebola.

Still, there's no need to panic:  Ebola doesn't spread through the air, and it's easily contained in sanitary conditions. Again:

And if that hasn't convinced you:

August 6, 2014: Breathe, America. The patient in New York is fine: