As Ebola's Spread Continues, Key Questions and Answers About Virus

Where did the disease come from, how does it spread, and can it mutate?

As the first patient diagnosed with Ebola outside of West Africa continues to receive treatment in a Dallas hospital—and as the deadly disease continues to spread in Liberia, Guinea, and Sierra Leone—more people are asking questions about the virus.

Is the United States really prepared to stop its spread? Can the virus be shared on the subway? Is it mutating?

This week, U.S. public health officials worked to allay fears about the disease's possible spread. The Centers for Disease Control and Prevention (CDC) is closely monitoring about 50 people who came into contact with the first Ebola patient to be diagnosed in the U.S., Thomas Eric Duncan.

Four of Duncan's close family members are now quarantined in the apartment where he fell ill. On Friday, an American cameraman working for NBC News was diagnosed with Ebola in Liberia and was being readied to fly back to the U.S. for treatment.

Amid growing anxiety, here are some key questions and answers about the virus:

What exactly is Ebola, anyway?

Ebola is a virus that causes fevers, severe gastrointestinal pain and, in many cases, unusual bleeding. Patients can die from fluid loss and organ shut-down.

Where did it come from—and when?

Ebola first emerged in small rural villages in central Africa in the mid-1970s. Researchers' best guess is that Ebola evolved in bats and spread to primates—including monkeys and people—who are exposed to bats' bodily fluids, like blood and feces. People can also get Ebola by touching or eating infected bats or primates.

How is Ebola spread?

Ebola is spread through contact with the bodily fluids of someone who is showing symptoms of the virus. Victims are not contagious until they begin showing symptoms, such as a fever. It is much less contagious than the common cold.

Most of those who have been infected have taken care of people who were ill or attended funerals for people who died of the virus. It is theoretically possible, but unlikely, to get Ebola from sharing a space with a sick person—say, by rubbing your hand against an armrest that someone with Ebola has recently sweated on and then touching your eyes.

Once someone has recovered from Ebola, with two tests over 24 hours showing no virus in the person's blood, they are no longer contagious and are believed to be immune to the disease, at least for an extended time. Ebola is present in semen and breast milk, and men who have recovered from the virus are told to use condoms during sex for the first seven weeks after recovery.

Could the virus mutate to become more contagious, say, by transmission through the air?

Viruses are very good at mutating, which can make them more or less dangerous. But researchers say it is highly unlikely that a virus would change its essential nature by becoming airborne instead of being passed through bodily fluids.

"At this point in time we have no evidence and do not anticipate that the Ebola virus is mutating to become airborne," the United Nations said in a statement on Friday. Instead of worrying about unlikely but theoretically possible outcomes, the UN said it's more important to address the known dangers of the current disease: "Energy needs to be focused on swiftly addressing the real needs and gaps in communities affected by this disease."

Why is Ebola so much worse this time than in previous outbreaks?

Since 1976, when it was first detected near the Ebola River in what is now the Democratic Republic of the Congo, Ebola has been largely confined to rural villages in central Africa. When officials heard of outbreaks, usually after just a handful of cases, they would quickly isolate patients and warn everyone who'd had recent contact with the person to get help at the first sign of symptoms.

The first known victim of the current outbreak was a 2-year-old in Guinea who died in December. But authorities did not hear of cases until March, by which point it had already spread. By late May, it was detected across Guinea's long, forested border with Sierra Leone, after people crossed to attend a funeral.

The bodies of people who have died from Ebola are highly contagious, and with burial traditions that include touching bodies, many people have become infected at funerals. Instead of staying within a small, isolated community, Ebola was quickly carried to capital cities, spreading rapidly through urban areas where people are in close contact with many others.

Because the number of patients was so high, medical facilities quickly became overwhelmed, and contacts at risk for the disease could not be tracked down and notified to be on guard for symptoms. The more people who got sick, died, and were buried, the more people who were infected at their funerals.

Making matters worse is that after years of civil war and corruption, the people of Liberia, Sierra Leone, and Guinea have learned to distrust authority figures. Instead of seeking medical attention when they fell ill, many people hid their illness, staying home and potentially infecting others.

Plus, medical facilities in the three West African nations are very basic—many lack electricity, running water, and basic equipment—so health care workers could do little to protect themselves from infection. More than 300 of them have gotten sick, and half have died.

Since May, new Ebola cases have been doubling every 20 to 30 days, and officials project that the epidemic could strike as many as 1.4 million people by the end of January if nothing more is done to stop it.

Why do health experts say it's unlikely to spread within the U.S.?

Every hospital in the United States is equipped to handle infectious patients, with gloves, gowns, and the cleaning supplies needed to wash away germs. Because there are not likely to be many Ebola cases in the United States, public health officials should be able to track down anyone who may have been exposed to the virus and warn them to track their temperatures and seek help at the first sign of symptoms. That's what's happening now in Dallas with Thomas Eric Duncan.

Beyond Duncan's family members, about 45 people with whom he came into contact over the four days he was showing symptoms—including the ambulance drivers and others he saw in the emergency room—are also being tracked and warned to watch for symptoms. In Nigeria and Senegal, these basic public health measures stopped the virus's spread, and no one has been diagnosed with Ebola in either country in more than three weeks.

To keep Americans safe, why can't we block all travelers from West Africa?

The United States has not imposed a travel ban out of fear that it will backfire, according to Thomas Frieden, director of the CDC. It would be virtually impossible to prevent everyone who wants to leave the three affected countries from doing so, and isolating the region would make it much harder to get volunteers to go in to help. The fastest way to reduce America's risk of Ebola is to end the epidemic in West Africa, he said.

Air travelers leaving the countries are screened to make sure they do not have fevers, which would indicate they were contagious if they had Ebola. Saudi Arabia has blocked all visitors from Liberia, Sierra Leone, and Guinea from attending this year's hajj, which is under way in Mecca, out of fear that a contagious illness could spread quickly among the more than one million pilgrims. (Related: "As Ebola Crisis Spreads in West Africa, Liberia's Deterioration Stands Out.")

How is Ebola treated?

There are no approved treatments specific to Ebola, though several are being developed and have been tested for the first time on patients in recent weeks. In West Africa, treatment is minimal and aimed primarily at keeping patients hydrated and relatively clean. About half of patients in the current outbreak die of the disease. (See "Doctors and Nurses Risk Everything to Fight Ebola in West Africa.")

The handful of patients treated in the United States so far have survived the disease after receiving aggressive care for their symptoms, including intravenous fluids and electrolytes; maintenance of oxygen levels and blood pressure; and treatments for other infections.

Has Ebola turned the corner in Africa?

The virus is still raging out of control in Liberia, Sierra Leone, and Guinea. According to the latest figures from the World Health Organization, as of October 1, 7,470 people have been diagnosed with Ebola in West Africa and 3,431 killed by the virus. The WHO has acknowledged that its official figures probably undercount the actual outbreak by a factor of 2 or 3, so the actual number of deaths could be approaching 10,000. Roughly 40 percent of those sickened by Ebola in West Africa have come down with the disease within the past three weeks. (Related: "Ebola Epidemic Could Top a Million Victims If Not Contained, CDC Warns.")

What can stop Ebola's spread?

The international community got more serious about helping end the outbreak in September, with the United States committing nearly $1 billion and authorizing 3,000 troops to go to the region to help with logistics. Help from other countries, including Cuba and China, and from the European Union is also beginning to arrive in West Africa.

It is unclear how long it will take to stop the outbreak, but official estimates range from six months to a year. Without the active involvement of the international community, the virus might never be brought under control, meaning people in West Africa would constantly be at risk, and could continue to spread the virus around the world.

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