CNN's Isha Sesay will be hosting a special coverage program about West Africa's Ebola outbreak on Monday, August 25. Tune in at 2.30pm ET / 7.30pm BST.

(CNN) -- Hundreds of people are dead as the worst Ebola virus outbreak in history sweeps through West Africa.

It began as a handful of cases in Guinea in March but quickly spread to neighboring Sierra Leone and Liberia.

Here are nine things to know about what the World Health Organization calls "one of the world's most virulent diseases."

Why does Ebola generate such fear?

Medecins Sans Frontieres (MSF) describes Ebola as "one of the world's most deadly diseases."

"It is a highly infectious virus that can kill up to 90% of the people who catch it, causing terror among infected communities," it says.

There is also no vaccination against it.

Of Ebola's five subtypes, the Zaire strain -- the first to be identified -- is considered the most deadly.

The WHO said preliminary tests on the Ebola virus in Guinea in March suggested that the outbreak there was this strain, though that has not been confirmed.

What is Ebola?

The Ebola virus causes viral hemorrhagic fever, which according to the U.S. Centers for Disease Control and Prevention (CDC), refers to a group of viruses that affect multiple organ systems in the body and are often accompanied by bleeding.

The virus is named after the Ebola River in the Democratic Republic of Congo (formerly Zaire), where one of the first outbreaks occurred in 1976. The same year there was another outbreak in Sudan.

The WHO says there are five different strains of the virus -- named after the areas they originated in. Three of these have been associated with large outbreaks of hemorrhagic fever in Africa.

These are the Bundibugyo -- an area of Uganda where the virus was discovered in 2007 -- Sudan and Zaire sub-types.

There has been a solitary case of Ivory Coast Ebola. This subtype was discovered when a researcher studying wild chimpanzees became ill in 1994 after an autopsy on one of the animals. The researcher recovered.

Finally, Reston Ebola is named after Reston in the U.S. state of Virginia, where this fifth strain of the Ebola virus was identified in monkeys imported from the Philippines. The CDC says while humans have been infected with Ebola Reston, there have been no cases of human illness or death from this sub-type.

What are Ebola's symptoms?

Early symptoms include sudden onset of fever, weakness, muscle pain, headaches and a sore throat. These symptoms can appear two to 21 days after infection.

The WHO says these nonspecific early symptoms can be mistaken for signs of diseases such as malaria, typhoid fever, meningitis or even the plague.

MSF says some patients may also develop a rash, red eyes, hiccups, chest pains and difficulty breathing and swallowing.

The early symptoms progress to vomiting, diarrhea, impaired kidney and liver function and sometimes internal and external bleeding.

Ebola can only be definitively confirmed by five different laboratory tests.

How is it treated?

There are no specific treatments for Ebola. MSF says patients are isolated and then supported by health care workers.

"This consists of hydrating the patient, maintaining their oxygen status and blood pressure and treating them for any complicating infections," it says.

There have been cases of health care workers contracting the virus from patients, and the WHO has issued guidance for dealing with confirmed or suspected cases of the virus.

Caregivers are advised to wear impermeable gowns and gloves and to wear facial protection such as goggles or a medical mask to prevent splashes to the nose, mouth and eyes.

MSF says it contained a 2012 outbreak in Uganda by placing a control area around its treatment center. An outbreak is considered over once 42 days -- double the incubation period of the disease -- have passed without any new cases.

What drugs exist to combat the disease?

Two American missionary workers infected with Ebola were given an experimental drug called ZMapp, which seems to have saved their lives. The drug, developed by a San Diego firm, had never been tried before on humans, but it showed promise in small experiments on monkeys.

But rolling out an untested drug during a massive outbreak would also be very difficult, according to MSF. Experimental drugs are typically not mass-produced, and tracking the success of such a drug if used would require extra medical staff where resources are already scarce. ZMapp's maker says it has very few doses ready for patient use.

There are other experimental drugs. Tekmira, a Vancouver-based company that has a $140 million contract with the U.S. Department of Defense to develop an Ebola drug, began Phase 1 trials with its drug in January. But the FDA recently halted the trial, asking for more information.

At least one potential Ebola vaccine has been tested in healthy human volunteers, according to Thomas Geisbert, a leading researcher at the University of Texas Medical Branch. And last week, the NIH announced that a safety trial of another Ebola vaccine will start as early as September.

And in March, the U.S. National Institutes of Health awarded a five-year, $28 million grant to establish a collaboration between researchers from 15 institutions who were working to fight Ebola.

"A whole menu of antibodies have been identified as potentially therapeutic, and researchers are eager to figure out which combinations are most effective and why," a news release about the grant said.

How does Ebola virus spread?

The WHO says it is believed that fruit bats may be the natural host of the Ebola virus in Africa, passing on the virus to other animals.

Humans contract Ebola through contact with the bodily fluids of infected animals or the bodily fluids of infected humans.

MSF says that while the virus is believed to be able to survive for some days in liquid outside an infected organism, chlorine disinfection, heat, direct sunlight, soaps and detergents can kill it.

MSF epidemiologist Kamiliny Kalahne said outbreaks usually spread in areas where hospitals have poor infection control and limited access to resources such as running water.

"People who become sick with it almost always know how they got sick: because they looked after someone in their family who was very sick -- who had diarrhea, vomiting and bleeding -- or because they were health staff who had a lot of contact with a sick patient," she said.

Can plane passengers become infected?

While the CDC acknowledges it's possible a person infected with Ebola in West Africa could get on a plane and arrive in another country, the chances of the virus spreading during the journey are low.

"It's very unlikely that they would be able to spread the disease to fellow passengers," said Stephen Monroe, deputy director of CDC's National Center for Emerging Zoonotic and Infectious Diseases.

"The Ebola virus spreads through direct contact with the blood, secretions, or other body fluids of ill people, and indirect contact -- for example with needles and other things that may be contaminated with these fluids."

He added that most people who have become infected with Ebola lived with or cared for an ill patient.

"This is not an airborne transmission," said Dr. Marty Cetron, director of CDC's Division of Global Migration and Quarantine. "There needs to be direct contact frequently with body fluids or blood."

Travelers should take precautions by avoiding areas experiencing outbreaks and avoid contact with Ebola patients.

"It is highly unlikely that someone suffering such symptoms would feel well enough to travel," IATA said in a statement.

"In the rare event that a person infected with the Ebola virus was unknowingly transported by air, WHO advises that the risks to other passengers are low. Nonetheless, WHO does advise public health authorities to carry out contact tracing in such instances."

This means determining who had contact with the affected person.

What should flight crew do if Ebola infection is suspected?

The CDC has issued guidance for airline crews on Ebola virus infections.

"As with many other global infectious disease outbreaks, airline carriers, crew members, airports can be very important partners in that front line," said Cetron. "Being educated, knowing the symptoms, recognizing what to do, having a response protocol, knowing who to call, those are really, really important parts of the global containment strategy to deal with threats like this."

The CDC advises that when flight crew members encounter a passenger with symptoms that they suspect could be Ebola, such as fever and bleeding, that they keep the sick person away from other passengers. They've been instructed to wear disposable gloves and to provide the sickened person with a surgical mask to prevent fluids from spreading through talking, sneezing or coughing.

The airline cleaning crew are also instructed to wear disposable gloves, wipe down surfaces including armrests, seat backs, trays and light switches. The CDC says that packages and cargo should not pose a risk, unless the items have been soiled with blood or bodily fluids.

When someone becomes ill on a flight, the captain is required by aviation regulations to report the suspected case to air traffic control, according to IATA.

What is the risk of catching Ebola on a plane?

How many cases have there been?

The CDC estimates there have been more than 3,000 cases of Ebola and more than 2,000 deaths since 1976.

The last recorded outbreaks before the current one in Guinea were in 2012 -- in Uganda and Democratic Republic of Congo.

The Uganda outbreak involved a total of 24 probable and confirmed cases, and 17 deaths, according to the WHO, which declared it had ended in October 2012.

MSF said the Uganda outbreak had been the Sudan strain, while the virus found in DRC was the Bundibugyo sub-type.

Before 2014, the most deadly outbreak was the 1976 outbreak in then Zaire, when 280 of 318 infected people died, according to the CDC. In 2000, there were 425 cases of Ebola Sudan in Uganda, which resulted in 224 fatalities.

埃博拉病毒：九事物了解的致命疾病
由蘇珊娜Cullinane和麥迪遜公園，美國有線電視新聞網
2014年8月25日 - 更新1518 GMT（2318 HKT）

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新聞提要
埃博拉病毒導致病毒性出血熱死亡率最高可達90％的人誰抓住它
它命名為埃博拉河在剛果民主共和國，在那裡首次爆發一次發生在1976年以後
症狀可以採取兩者之間的21天出現受害者感染病毒後，
通過與被感染的動物或人的體液接觸人類合同埃博拉
CNN的宵塞薩伊將舉辦約在週一，8月25日調在美東時間下午2:30 /下午7:30 BST西部非洲的埃博拉出血熱疫情專題報導節目。
（CNN） -數以百計的人死亡的最嚴重的埃博拉病毒爆發的歷史席捲西非。
它開始作為三月份屈指可數的幾例，但很快蔓延到鄰國塞拉利昂和利比里亞。
這裡有9件事了解一下世界衛生組織稱之為“世界上最致命的疾病之一。”
為什麼埃博拉病毒產生這種恐懼？
無國界醫生組織（MSF）描述埃博拉病毒為“世界上最致命的疾病之一。”
“這是一種傳染性很強的病毒，可以殺死高達90％誰抓住它，造成感染社區中製造恐怖的人，”它說。
也有反對沒有接種疫苗。
埃博拉病毒的五個亞型，扎伊爾毒株 - 第一個被確定的 - 被認為是最致命的。
世衛組織說，在埃博拉病毒在幾內亞在三月份的初步測試表明，該疫情有這樣的壓力，雖然這還沒有得到證實。
什麼是伊波拉病毒？
埃博拉病毒導致病毒性出血熱，而根據美國疾病控制和預防中心（CDC）的，指的是一組累及多個器官系統在體內，往往伴有出血病毒。
埃博拉河在剛果民主共和國（前扎伊爾），其中第一個爆發的一次發生在1976年同一年出現了在蘇丹再次爆發後，該病毒被命名。
世衛組織說，有五種不同品系的病毒 - 它們起源於其中三個已與大暴發非洲出血熱相關的領域而得名。
這些都是本迪布焦 - 烏干達該病毒被發現於2007年的區域 - 蘇丹和扎伊爾的子類型。
已經有科特迪瓦埃博拉病毒的一個孤立的情況下，這種亞型被發現的動物之一進行屍檢後，在1994年時，研究人員研究野生黑猩猩卻病倒了。研究人員恢復。
最後，雷斯頓伊波拉病毒是萊斯頓的名字命名的弗吉尼亞州的美國州，那裡的埃博拉病毒第五菌株在從菲律賓進口的猴子識別。疾病預防控制中心說，雖然人類已經感染了埃博拉萊斯頓，沒有出現過例人患病或死亡的這一分型。
什麼是埃博拉病毒的症狀？
早期症狀包括突然發燒，無力，肌肉疼痛，頭痛和喉嚨痛。這些症狀可以感染後會出現2〜21天。
世衛組織說，這些非特異性的早期症狀可被誤認為是疾病的徵兆，如瘧疾，傷寒，腦膜炎，甚至瘟疫。
無國界醫生表示，部分患者也可出現皮疹，眼睛發紅，打嗝，胸痛和呼吸困難和吞嚥。
早期症狀發展為嘔吐，腹瀉，損害腎臟和肝臟功能，有時內部和外部出血。
埃博拉只能由五個不同的實驗室測試來明確證實。
如何治療？
有沒有針對具體的埃博拉病毒治療。無國界醫生表示，病人被隔離，然後由醫護人員的支持。
“這包括保濕病人，保持其氧狀態和血壓和對待他們的任何複雜性感染，”它說。
已經有醫護人員病例患者感染病毒，以及世界衛生組織已發出處理病毒的確診或疑似病例的指導。
照顧者宜戴不透水的禮服和手套，穿防護面部，如護目鏡或外科口罩，以防止飛濺的鼻子，嘴巴和眼睛。
無國界醫生組織說，它包含了2012年的爆發在烏干達放置一個控制區域圍繞其治療中心。爆發被認為是在一次42日 - 雙倍的疾病的潛伏期 - 已經過去了，沒有任何新的病例。
什麼藥物存在打擊diseas é ？
感染埃博拉兩名美國傳教士工人正在給一種實驗性藥物稱為ZMapp，這似乎已經救了他們的性命。藥物，由聖地亞哥公司開發的，以前從未嘗試過的人，但它表現出承諾，在猴子身上的實驗小。
但大規模爆發期間推出了未經測試的藥物也將是非常困難的，根據無國界醫生。試驗藥物通常不是大量生產，並跟踪如果使用的話就需要額外的醫務人員在資源已經稀缺的這種藥物的成功。ZMapp的製造商表示，它已經極少劑量的準備患者使用。
還有其他的實驗性藥物。Tekmira，溫哥華的公司，擁有1.4億美元合同與美國國防部部制定了埃博拉病毒的藥物，開始第1階段臨床試驗用藥物的一月。但是，FDA最近停止了試驗，要求獲得更多信息。
至少有一個潛在的埃博拉病毒疫苗在健康志願者進行了測試，按照托馬斯Geisbert，在德州大學醫療分部的主要研究員。上週，在美國國立衛生研究院宣布，安全性試驗的另一個埃博拉疫苗最快將在九月開始。
而在三月份，美國衛生研究院國家頒發的五年，28000000美元撥款，以確定誰正在努力爭取埃博拉從15個機構的研究人員之間的合作。
“抗體的整個菜單已被確定為潛在的治療和研究人員都急於找出哪些組合是最有效的，以及為什麼，”關於授予一個新聞發布會上說。
如何埃博拉病毒 傳播的？
世衛組織說，它認為果蝠可能是埃博拉病毒在非洲的自然宿主，通過對病毒傳播給其他動物。
人類合同埃博拉通過與受感染的動物的體液或感染人的體液接觸。
無國界醫生表示，雖然該病毒被認為是能夠在液體中存活數天被感染的生物，氯消毒，高溫，陽光直射，肥皂外和清潔劑可以殺死它。
無國界醫生流行病學Kamiliny Kalahne說爆發通常散佈在醫院有窮感染控制和有限的訪問，如自來水資源的地區。
“誰生病了它的人幾乎都知道他們是怎麼生病了：因為他們看起來有人在他們的家庭誰是病得很重之後 - 誰了腹瀉，嘔吐和出血 - 或者因為他們是醫務人員誰有很多接觸有一個生病的病人，“她說。
飛機的乘客可能被感染？
而疾控中心承認它可能感染了埃博拉病毒在西非能拿在一個平面上，並在另一個國家到達一個人，該病毒在旅途中傳播的可能性很小。
“這是非常不可能的，他們將能夠把疾病傳播給其他乘客，” 斯蒂芬·夢露，CDC的國家中心的新興人畜共患傳染病副主任說。
“埃博拉病毒傳播通過與血液，分泌物，或患病的人的其他體液，以及間接接觸的直接接觸 - 例如用針和可與這些流體被污染的其他東西。”
他補充說，誰已成為感染埃博拉大多數人居住或照顧生病的病人。
“這不是空氣傳播，”馬蒂·塞特龍博士，全球移民和檢疫疾病預防控制中心的部門主任。“有需要經常會直接接觸體液或血液。”
旅客應採取預防措施，避免疫情暴發地區，並避免與埃博拉病毒的病人接觸。
“這是極不可能的，一個人患這種症狀會覺得不夠好去旅行，” 國際航空運輸協會在一份聲明中說。
“在極少數情況下感染了埃博拉病毒的人在不知不覺中被空運，世衛組織建議，對其他乘客的風險較低。 然而，誰不建議公共衛生部門進行 接觸者追踪在這種情況下。“
這意味著決定誰曾與受影響的人接觸。
我應該機組人員做，如果感染埃博拉病毒被懷疑？
疾病預防控制中心發布了對埃博拉病毒感染飛機機組人員的指導。
“與許多其他全球性傳染病爆發，航空運營商，機組人員，機場可在前線非常重要的合作夥伴，”塞特龍說。“受教育，知道了症狀，認識該怎麼做，有一個響應協議，知道給誰打電話，這些都是真的，在全球遏制戰略中非常重要的部分，以對付這樣的威脅。”
疾病預防控制中心建議，當飛行機組成員遇到的症狀，他們懷疑可能是埃博拉病毒，如發熱，出血，使他們保持病人遠離其他乘客乘客。他們已經責成戴一次性手套，並提供生病的人使用口罩，以防止流體通過說話傳播，打噴嚏或咳嗽。
該航空公司的清潔人員也責成戴一次性手套，擦拭表面，包括扶手，座椅靠背，托盤和燈的開關。疾病預防控制中心表示，包和貨物應該不會構成危險，除非該項目已被弄髒血液或體液。
當有人生病了在飛機上，機長必須通過航空規定報告的疑似病例空中交通管制，根據國際航空運輸協會。
什麼是在一個平面上醒目埃博拉病毒的風險？
有多少案件存在了？
在CDC估計已經有3000多例埃博拉和2000多人死亡從1976年開始。
最後記錄的爆發當前的幾內亞前均在2012年 - 在烏干達和剛果民主共和國。
烏干達爆發共24可能和確診病例，17人死亡參與，根據世界衛生組織，宣布它在2012年10月結束。
無國界醫生組織說，烏干達爆發過蘇丹緊張，而在剛果（金）發現了該病毒是本迪布焦亞類型。
在2014年，最致命的爆發是在1976年爆發在當時的扎伊爾，當感染者318人280死了，根據疾病預防控制中心。在2000年，有425​​宗伊波拉蘇丹，烏干達，導致224人死亡的。