The Ebola outbreak shows no signs of stopping as cases are expected to reach 20,000 in the next six months.
The virus has already killed 1,552 people in Liberia, Guinea, Sierra Leone and Nigeria, according to the World Health Organization. In fact, a little more than half of all Ebola deaths recorded since the virus' discovery in 1976 have occurred in the last five months, according to WHO data.
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Here are 10 things you should know about the outbreaks as fears continue to mount in Africa and beyond.
Ebola Cases Expected to Top 20,000
More than 3,000 Ebola cases have been reported since March, but the World Health Organization said Thursday that it expects cases to exceed 20,000 in the next six months.
The Ebola outbreak is already the deadliest on record, and WHO officials say the impact may be far worse than reported.
The number of known infections -- currently 3,069 -- is likely fewer than the actual number of infections because of those who hide the infected and bury the dead in secret, WHO said in a statement on Aug. 22. The number also excludes so-called "shadow zones" that are rumored to have Ebola cases that go unconfirmed because of community resistance and a lack of medical staff, the agency said.
Health officials also suspect an "invisible caseload" in Liberia because new treatment facilities are filling with previously unidentified Ebola patients as soon as they open.
Ebola Toll May 'Vastly Underestimate' Crisis
Five Researchers Die Studying Ebola Genome
Dozens of researchers teamed up track how the Ebola virus has mutated over time. Compared to previous strains, it has mutated more than 300 times, including 50 times since March.
They also found that a Guinea healer's funeral in May seemed to have been a turning point in the outbreak, infecting mourners before the outbreak blew up, according to the Associated Press.
Nearly 60 researchers set out to sequence the Ebola genome, but five of them died before the study was published in the journal Science on Thursday. The researchers who died were all affiliated with the Kenema Government Hospital in Sierra Leone.
Senegal Reports First Ebola Case
The Senegalese Health Ministry has reported its first Ebola case, a Guinean student who had been in contact with sick people in Guinea and was later hospitalized in Senegal. The Guinea government said it had lost track of him three weeks ago, according to the Associated Press. The student has since been quarantined and tested positive for Ebola.
Earlier this week, the Democratic Republic of Congo -- 800 miles from the Ebola outbreak in West Africa -- reported 24 suspected Ebola cases, including 13 deaths. None of the patients or their close contacts had traveled to West Africa, according to WHO.
"At this time, it is believed that the outbreak in [the Democratic Republic of Congo] is unrelated to the ongoing outbreak in West Africa," the agency said in a statement today, adding that samples from the Congo cases are currently being tested for the virus.
The first known case in Congo occurred in a pregnant woman who became ill after butchering a "bush animal" that her husband killed, according to WHO. She died on Aug. 11. Health care workers who tended to her, including a doctor, two nurses and a ward boy, developed similar symptoms and died, the agency said.
Ebola was first discovered in the Congo in 1976 and is named for the Ebola River.
U.S. Hospitals and Colleges Taking No Chances
College administrations will be screening students from West Africa for Ebola, according to the Associated Press. Some are testing students' temperatures and having private discussions with them about travel history.
Hospitals and state labs across the country recently have reported dozens of possible Ebola cases to the U.S. Centers for Disease Control and Prevention. Only 10 patients raised CDC's concerns enough to test their blood for the virus, and all of the results have come back negative so far, CDC officials told ABC News last week.
Potential Ebola patients at Mount Sinai Hospital in New York, Johns Hopkins Medicine in Maryland, University of New Mexico Hospital in Albuquerque and an undisclosed hospital in Ohio have also tested negative for Ebola over the past several weeks.
The CDC had sent a health alert to hospitals across the country urging them to ask patients about their travel history to help identify potential Ebola cases.
ZMapp Cured 18 Monkeys in New Study
While there's currently no cure for Ebola, a new study found that 18 monkeys given the experimental drug ZMapp up to five days after exposure to the virus survived. Three monkeys who did not receive the drug died eight days after exposure, according to the study published Aug. 29 in the journal Nature.
At least six people have received ZMapp: American health workers Dr. Kent Brantly and Nancy Writebol, a Spanish priest, two African doctors and one African nurse. Brantly and Writebol survived but the Spanish priest and one of the African doctors did not. The remaining African ZMapp recipients are expected to be discharged from the hospital on Aug. 29.
Still, experts say it's unclear whether ZMapp -- a cocktail of three antibodies that attack the virus -- actually helped those who received it.
"Frankly we do not know if it helped them, made any difference, or even delayed their recovery," said Dr. Bruce Ribner, director of Emory University Hospital's infectious disease unit, where Brantly and Writebol were treated.
Experimental Ebola Drug's Role in Americans' Recoveries Remains Unclear
1 in 4 Americans Fears Ebola Outbreak, Poll Shows
About a quarter of Americans fear that they or someone in their family will come down with Ebola in the next year, according to a Harvard School of Public Health poll published Aug. 21.
Harvard and SSRS, an independent research company, conducted the poll of 1,025 adults and found that 39 percent of respondents feared a large Ebola outbreak in the United States.
According to the poll, 68 percent of Americans thought the disease could spread "easily" and 33 percent said they thought there was an available treatment for it, both highlighting a lack of understanding about Ebola in this country. In reality, the virus is only transmitted through contact with body fluids like blood and urine, and there is no cure. It's unclear whether ZMapp, the unofficial drug given to the American Ebola patients, helped or hindered their recovery, experts say.
Officials Request Exit Screenings at Airports, Seaports
The World Health Organization has requested exit screenings at international airports, seaports and land crossings in all countries affected by the Ebola outbreak.
"Any person with an illness consistent with [Ebola virus disease] should not be allowed to travel unless the travel is part of an appropriate medical evacuation," WHO said in a statement. "There should be no international travel of Ebola contacts or cases, unless the travel is part of an appropriate medical evacuation."
Ebola symptoms include fever, weakness, muscle pain and sore throat before they progress to vomiting, diarrhea and rash. Some people may also experience bleeding.
The WHO Ebola Emergency Committee advised against international travel or trade restrictions.
Governments Are Reviving the 'Cordon Sanitaire'
Officials from Guinea, Sierra Leone and Liberia have implemented a "cordon sanitaire" or sanitary barrier -- a cross-border isolation zone designed to contain people with the highest infection risk.
The tactic, used to prevent the spread of plague in medieval times, literally blocks off an area thought to contain 70 percent of the epidemic. But some experts say there's little proof that isolation zones can prevent the spread of disease.
Ebola-Stricken Countries Turning to Ancient Practice to Curb Outbreak
"It may not be sufficiently structured so it can prevent people from leaving," said Dr. William Schaffner, an infectious disease expert at Vanderbilt Medical Center in Nashville, Tennessee.
Fearful Communities Are Shunning Survivors
An estimated 49 percent of people infected in the outbreak have survived the virus, according to WHO data. But they face fear and shame from their communities.
Survivor Sulaiman Kemokai, from Sierra Leone, said people in his community are afraid to touch him even though he's been declared virus-free, the Associated Press reported.
Ebola Survivor Shunned by Boyfriend, School
The Ebola virus can only be spread through contact with bodily secretions such as blood, urine or sweat. But misinformation is rampant in areas hardest hit by the virus, health officials said.
FDA Warns Against Fake Ebola Treatments
The U.S. Food and Drug Administration is warning people to avoid fake Ebola treatments and vaccines being sold online. The agency said products claiming to protect people from the infection began popping up online after the outbreak began in March.
"There are currently no FDA-approved vaccines or drugs to prevent or treat Ebola," the agency said in a statement. "Although there are experimental Ebola vaccines and treatments under development, these investigational products are in the early stages of product development, have not yet been fully tested for safety or effectiveness, and the supply is very limited."
"There are no approved vaccines, drugs, or investigational products specifically for Ebola available for purchase on the Internet," the FDA added. "By law, dietary supplements cannot claim to prevent or cure disease."
Ebola Outbreak Spreads: Senegal Reports 1st Case