Story highlights Unlike a cold or the flu, Ebola cannot be transmitted before symptoms show up

CDC director: All passengers boarding from Ebola hotspots are screened for fever

A man being treated for Ebola in Dallas had symptoms for about 4 days before he was isolated

CDC team trying to find those who came in contact with him; will monitor them for symptoms

The unidentified man, who is being treated at a Dallas hospital, didn't show symptoms until several days after he arrived in the United States from Liberia.

Officials are tight-lipped about how he contracted the virus or how he's being treated, citing privacy concerns.

But shortly after the news broke Tuesday evening, more than 50,000 tweets about Ebola flew through Twitter in a one-hour period, many of them panicked responses.

Should we be concerned?

The short answer: no.

Now let's get to the long answer.

Could the patient's fellow passengers be infected?

The patient being treated in Texas flew from one of the Ebola hot zones -- Liberia -- to Dallas.

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But his fellow passengers aren't thought to be at risk because you can only contract Ebola through direct contact with the bodily fluids of someone who's actively sick with it.

It's not like a cold or the flu, which can be spread before symptoms show up. And it doesn't spread through the air.

"It's very unlikely that (Ebola victims) would be able to spread the disease to fellow passengers," said Stephan Monroe of the Centers for Disease Control and Prevention.

What's to stop other Ebola patients from getting on a flight and coming here?

The CDC has issued warnings to avoid nonessential travel to Liberia, Sierra Leone and Guinea , the countries hit the hardest by the outbreak.

And it's also working with airport officials in those nations, and in Nigeria, so every person getting on a plane is screened for fever.

"And if they have a fever, they are pulled out of the line, assessed for Ebola and don't fly unless Ebola is ruled out," CDC Director Dr. Thomas Frieden said.

How do airport authorities know what to look for?

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Those stricken with Ebola suffer ghastly symptoms -- including vomiting, diarrhea, muscle pain, fever and unexplained bleeding.

That's part of the reason why the odds of getting Ebola from plane passengers is very low, the International Air Transport Association said.

"It is highly unlikely that someone suffering such symptoms would feel well enough to travel."

What's being done when the planes land in the U.S.?

The United States isn't planning on banning flights coming from the hot zones in West Africa, White House spokesman Josh Earnest said in August.

But once flights land at a U.S. airport from one of those countries, passengers are screened again.

"And there are facilities available that if an individual is detected exhibiting these symptoms, that they can be quarantined and promptly evaluated by a medical professional," Earnest said.

Are those procedures being followed?

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CNN Senior Medical Correspondent Elizabeth Cohen said when she and two colleagues recently returned from reporting in Liberia, they got a mixed bag of responses from Customs and Border Protection officers.

"We all said we were journalists who had just been in Liberia covering Ebola," Cohen said. "One of my colleagues was told, 'Oh, OK, welcome back home, sir' -- and (was) just let in -- that was it."

Cohen herself got a different response.

"I was told, 'Wait a minute, I think I got an email about this,' and the border patrol officer went and consulted with his colleagues," Cohen said.

That officer later told her she should check her system for 21 days.

"I said, 'What should I be checking?' And he wasn't sure," Cohen said.

The third colleague merely had his boots checked to see if there was mud on them.

"Three very different responses. They can't all be the way to do it," Cohen said. "I was surprised at how sort of chaotic it felt."

So, how did Dallas patient slip through?

The Ebola patient in Dallas didn't start showing symptoms until several days after he landed in the United States, Frieden said.

Isn't he putting others at risk?

Photos: The Ebola epidemic Photos: The Ebola epidemic An Ebola survivor participates in a study in Monrovia, Liberia, on June 17, 2015. The country launched a five-year study to unravel the mystery of the long-term health effects that plague survivors of the viral disease. Since the epidemic started more than a year ago in a remote village in Guinea, more than 11,000 people have died, the vast majority in three West African nations, according to the latest numbers from the World Health Organization . And that number is believed to be low, since there was widespread under-reporting of cases, according to WHO. Hide Caption 1 of 45 Photos: The Ebola epidemic Women in Monrovia celebrate after the World Health Organization declared Liberia Ebola-free on May 9, 2015. Other cases have recurred since, however. Two people in Liberia have died of the disease since the end of June, just weeks after the WHO declared the nation free of the disease. Hide Caption 2 of 45 Photos: The Ebola epidemic A man walks past an Ebola awareness painting in Monrovia on March 22, 2015. Hide Caption 3 of 45 Photos: The Ebola epidemic Soldiers from the U.S. Army's 101st Airborne Division walk across the tarmac at Campbell Army Airfield before reuniting with their families at a homecoming ceremony March 21, 2015 in Fort Campbell, Kentucky. The 162 soldiers were deployed in Liberia, where they helped fight the spread of Ebola. Hide Caption 4 of 45 Photos: The Ebola epidemic Relatives weep for a loved one who it was believed died from Ebola, at a graveyard on the outskirts of Monrovia on March 11, 2015. Hide Caption 5 of 45 Photos: The Ebola epidemic Doctors Without Borders staffer Alex Eilert Paulsen watches as mattresses and bed frames burn at the Ebola Treatment Unit in Paynesville, Liberia, on January 31, 2015. The organization reduced its number of beds from 250 to 30 as gains were made in battling the virus. Hide Caption 6 of 45 Photos: The Ebola epidemic Pauline Cafferkey, a Scottish woman diagnosed with Ebola, is put on a plane in Glasgow, Scotland, on December 30, 2014. Cafferkey, a 39-year-old nurse who volunteered in Sierra Leone, was being transported to London for treatment. Hide Caption 7 of 45 Photos: The Ebola epidemic A child who survived the Ebola virus is fed by another survivor at a treatment center on the outskirts of Freetown, Sierra Leone, on November 11, 2014. Hide Caption 8 of 45 Photos: The Ebola epidemic Health workers in Monrovia cover the body of a man suspected of dying from the Ebola virus on October 31, 2014. Hide Caption 9 of 45 Photos: The Ebola epidemic Kaci Hickox leaves her home in Fort Kent, Maine, to take a bike ride with her boyfriend on October 30, 2014. Hickox, a nurse, recently returned to the United States from West Africa, where she treated Ebola victims. State authorities wanted her to avoid public places for 21 days -- the virus' incubation period. But Hickox, who twice tested negative for Ebola, said she would defy efforts to keep her quarantined at home. Hide Caption 10 of 45 Photos: The Ebola epidemic Health officials in Nairobi, Kenya, prepare to screen passengers arriving at the Jomo Kenyatta International Airport on October 28, 2014. Hide Caption 11 of 45 Photos: The Ebola epidemic U.S. President Barack Obama hugs Ebola survivor Nina Pham in the Oval Office of the White House on October 24, 2014. Pham, one of two Dallas nurses diagnosed with the virus, was declared Ebola-free after being treated at a hospital in Bethesda, Maryland. The other nurse, Amber Vinson (not pictured), was treated in Atlanta and also declared Ebola-free. Hide Caption 12 of 45 Photos: The Ebola epidemic Health workers in Port Loko, Sierra Leone, transport the body of a person who is suspected to have died of Ebola on October 21, 2014. Hide Caption 13 of 45 Photos: The Ebola epidemic Health workers bury a body on the outskirts of Monrovia on October 20, 2014. Hide Caption 14 of 45 Photos: The Ebola epidemic Garteh Korkoryah, center, is comforted during a memorial service for her son, Thomas Eric Duncan, on October 18, 2014, in Salisbury, North Carolina. Duncan, a 42-year-old Liberian citizen, died October 8 in a Dallas hospital. He was in the country to visit his son and his son's mother, and he was the first person in the United States to be diagnosed with Ebola. Hide Caption 15 of 45 Photos: The Ebola epidemic Boys run from blowing dust as a U.S. military aircraft leaves the construction site of an Ebola treatment center in Tubmanburg, Liberia, on October 15, 2014. Hide Caption 16 of 45 Photos: The Ebola epidemic Aid workers from the Liberian Medical Renaissance League stage an Ebola awareness event October 15, 2014, in Monrovia. The group performs street dramas throughout Monrovia to educate the public on Ebola symptoms and how to handle people who are infected with the virus. Hide Caption 17 of 45 Photos: The Ebola epidemic Ebola survivors prepare to leave a Doctors Without Borders treatment center after recovering from the virus in Paynesville, Liberia, on October 12, 2014. Hide Caption 18 of 45 Photos: The Ebola epidemic A man dressed in protective clothing treats the front porch of a Dallas apartment on October 12, 2014. The apartment is home to one of the two nurses who were diagnosed with Ebola after treating Thomas Eric Duncan, a Liberian national who traveled to Dallas and later died from the virus. Hide Caption 19 of 45 Photos: The Ebola epidemic A woman crawls toward the body of her sister as a burial team takes her away for cremation October 10, 2014, in Monrovia. The sister had died from Ebola earlier in the morning while trying to walk to a treatment center, according to her relatives. Hide Caption 20 of 45 Photos: The Ebola epidemic A man digs a grave on October 7, 2014, outside an Ebola treatment center near Gbarnga, Liberia. Hide Caption 21 of 45 Photos: The Ebola epidemic A person peeks out from the Dallas apartment where Thomas Eric Duncan, the first person diagnosed with the Ebola virus in the United States, was staying on October 3, 2014. Hide Caption 22 of 45 Photos: The Ebola epidemic A girl cries as community activists approach her outside her Monrovia home on October 2, 2014, a day after her mother was taken to an Ebola ward. Hide Caption 23 of 45 Photos: The Ebola epidemic A health official uses a thermometer September 29, 2014, to screen a Ukrainian crew member on the deck of a cargo ship at the Apapa port in Lagos, Nigeria. Hide Caption 24 of 45 Photos: The Ebola epidemic Workers move a building into place as part of a new Ebola treatment center in Monrovia on September 28, 2014. Hide Caption 25 of 45 Photos: The Ebola epidemic Medics load an Ebola patient onto a plane at Sierra Leone's Freetown-Lungi International Airport on September 22, 2014. Hide Caption 26 of 45 Photos: The Ebola epidemic A few people are seen in Freetown during a three-day nationwide lockdown on September 21, 2014. In an attempt to curb the spread of the Ebola virus, people in Sierra Leone were told to stay in their homes. Hide Caption 27 of 45 Photos: The Ebola epidemic Supplies wait to be loaded onto an aircraft at New York's John F. Kennedy International Airport on September 20, 2014. It was the largest single shipment of aid to the Ebola zone to date, and it was coordinated by the Clinton Global Initiative and other U.S. aid organizations. Hide Caption 28 of 45 Photos: The Ebola epidemic A child stops on a Monrovia street September 12, 2014, to look at a man who is suspected of suffering from Ebola. Hide Caption 29 of 45 Photos: The Ebola epidemic After an Ebola case was confirmed in Senegal, people load cars with household items as they prepare to cross into Guinea from the border town of Diaobe, Senegal, on September 3, 2014. Hide Caption 30 of 45 Photos: The Ebola epidemic A health worker wearing a protective suit conducts an Ebola prevention drill at the port in Monrovia on August 29, 2014. Hide Caption 31 of 45 Photos: The Ebola epidemic A burial team from the Liberian Ministry of Health unloads bodies of Ebola victims onto a funeral pyre at a crematorium in Marshall, Liberia, on August 22, 2014. Hide Caption 32 of 45 Photos: The Ebola epidemic Dr. Kent Brantly leaves Emory University Hospital on August 21, 2014, after being declared no longer infectious from the Ebola virus. Brantly was one of two American missionaries brought to Emory for treatment of the deadly virus. Hide Caption 33 of 45 Photos: The Ebola epidemic An Ebola Task Force soldier beats a local resident while enforcing a quarantine on the West Point slum on August 20, 2014. Hide Caption 34 of 45 Photos: The Ebola epidemic Local residents gather around a very sick Saah Exco, 10, in a back alley of the West Point slum on August 19, 2014. The boy was one of the patients that was pulled out of a holding center for suspected Ebola patients after the facility was overrun and closed by a mob on August 16. A local clinic then refused to treat Saah, according to residents, because of the danger of infection. Although he was never tested for Ebola, Saah's mother and brother died in the holding center. Hide Caption 35 of 45 Photos: The Ebola epidemic Workers prepare the new Ebola treatment center on August 17, 2014. Hide Caption 36 of 45 Photos: The Ebola epidemic Liberian police depart after firing shots in the air while trying to protect an Ebola burial team in the West Point slum of Monrovia on August 16, 2014. A crowd of several hundred local residents reportedly drove away the burial team and their police escort. The mob then forced open an Ebola isolation ward and took patients out, saying the Ebola epidemic is a hoax. Hide Caption 37 of 45 Photos: The Ebola epidemic A health worker disinfects a corpse after a man died in a classroom being used as an Ebola isolation ward August 15, 2014, in Monrovia. Hide Caption 38 of 45 Photos: The Ebola epidemic Aid worker Nancy Writebol, wearing a protective suit, gets wheeled on a gurney into Emory University Hospital in Atlanta on August 5, 2014. A medical plane flew Writebol from Liberia to the United States after she and her colleague Dr. Kent Brantly were infected with the Ebola virus in the West African country. Hide Caption 39 of 45 Photos: The Ebola epidemic Members of Doctors Without Borders adjust tents in the isolation area in Kailahun on July 20, 2014. Hide Caption 40 of 45 Photos: The Ebola epidemic Boots dry in the Ebola treatment center in Kailahun on July 20, 2014. Hide Caption 41 of 45 Photos: The Ebola epidemic Dr. Jose Rovira of the World Health Organization takes a swab from a suspected Ebola victim in Pendembu, Sierra Leone, on July 18, 2014. Hide Caption 42 of 45 Photos: The Ebola epidemic Red Cross volunteers disinfect each other with chlorine after removing the body of an Ebola victim from a house in Pendembu on July 18, 2014. Hide Caption 43 of 45 Photos: The Ebola epidemic A scientist separates blood cells from plasma cells to isolate any Ebola RNA and test for the virus April 3, 2014, at the European Mobile Laboratory in Gueckedou, Guinea. Hide Caption 44 of 45 Photos: The Ebola epidemic Health specialists work March 31, 2014, at an isolation ward for patients at the facility in southern Guinea. Hide Caption 45 of 45

The paramedics who took the patient to the hospital have been isolated, the chief of staff for Dallas Mayor Mike Rawlings told CNN. They have not shown symptoms of the disease so far.

The ambulance that carried the patient -- ambulance No. 37 -- was in use for two days after the transport but was properly decontaminated, said Dallas city spokeswoman Sana Syed.

Frieden said the patient himself had a handful of contacts with people after he fell ill and before he was isolated -- a period of about four days.

A CDC team arrived in Texas to investigate the people who came in contact with the man. Those people will be monitored for 21 days to see if they develop symptoms. If they do, they'll be isolated.

"It is certainly possible that someone who had contact with this individual could develop Ebola in the coming weeks," Frieden said. "But there is no doubt in my mind that we will stop it here."

How is this not concerning?

Although there's no vaccine and no cure, the one real advantage we have with Ebola is that doctors know how to control it.

Ebola isn't "some mystical pathogen (with) some bizarre mode of transmission," said Bruce Ribner , director of Emory University Hospital's Infectious Disease Unit.

And we have the resources to contain it.

How are we so confident?

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For starters, the United States has the luxury of better health care compared to Liberia, Sierra Leone and Guinea.

The U.S. has facilities that can "do the kind of isolation that apparently is very difficult to do within the health care infrastructure in the African countries that we are talking about," said Dr. Anthony Fauci of the National Institutes of Health.

Secondly, remember Kent Brantly and Nancy Writebol? The doctor and the American missionary were infected in Liberia, brought to Atlanta's Emory University Hospital, placed in isolation units, treated and discharged.

They were the first humans with Ebola to ever arrive in the United States. And they are now fine.