An expanding Ebola outbreak in the Democratic Republic of the Congo (DRC) and Uganda has prompted experts at the World Health Organization to declare a “public health emergency of international concern,” and U.S. officials are trying to halt the spread of Ebola to the U.S. by blocking travelers from high-risk countries.

U.S. health officials have invoked what’s known as Title 42 of the Public Health Act to bar travelers who have recently been in Uganda, South Sudan or the DRC from entering the U.S.

Federal officials invoked Title 42 during the COVID-19 pandemic and also have used the measure to prevent immigrants from specific countries from entering the U.S.

Ebola is particularly frightening because there are not vaccines for most strains, nor are there cures. When people are dying of Ebola, they start bleeding from multiple parts of the body. The illness spreads through bodily fluids, so Ebola can become highly infectious when patients are severely ill.

Health officials in Africa say at least 338 people — including an American doctor who has been working in the region — are suspected of having Ebola. So far, 13 cases have been confirmed, and an estimated 89 people have died. But the outbreak is growing fast, so health officials expect the number of people who are affected to keep climbing.

The current Ebola illnesses stem from an unusual strain of the disease, and the area of the DRC where the cases have emerged has been marred by violence. So, health officials have had a hard time testing people and taking actions to halt the spread of Ebola. American officials also dismantled USAID, a longtime U.S. program that provided extensive support for public health programs in Africa and around the world.

U.S. officials said that they will deploy experts from the U.S. Centers for Disease Control and Prevention (CDC) to help contain the Ebola outbreak in the DRC. U.S. officials also will work to help affected Americans.

The U.S. doctor developed Ebola symptoms while caring for patients in the DRC. He tested positive for the Ebola Bundibugyo strain of the virus on May 17 after developing symptoms over the weekend. CDC officials said they are working with officials from the U.S. Department of State to bring the doctor to Germany so he can receive care there. Family members and others who were in close contact with the doctor also will be transported to Germany.

There is no vaccine for the Budibugyo strain of Ebola, and treatment focuses on supportive care and ensuring that patients have plenty of fluids. Historically, this strain of Ebola has a high mortality rate, causing deaths in about one quarter to one half of people who get the illness.

While the risk of Ebola spreading in the U.S. remains extremely low, health experts are closely monitoring the outbreak and have plans in place in case a suspected case emerges in the U.S.

To answer key questions about Ebola, we consulted with Dr. Michelle Barron, senior medical director of infection prevention and control at UCHealth and one of Colorado’s top infectious disease experts.

Why is Ebola so frightening?

“Mortality is high,” Barron said. “Somewhere between 25 and 50% of people who get it die. So, this is not insignificant.”

Should the average person in the U.S. be worried about Ebola?

No. The average person in the U.S. doesn’t need to worry about Ebola.

“The likelihood of us seeing a patient is low. But if we did, we have many trained people with a lot of experience to manage this appropriately,” said Barron, who is also a professor at the University of Colorado Anschutz School of Medicine.

When was Ebola last a concern in the U.S.?

A relatively small Ebola outbreak emerged in 2022 in Uganda. That outbreak was tied to the Sudan strain of the virus.

While there were no confirmed cases in the U.S., federal, state and local health officials monitored some travelers arriving from affected areas.

In Colorado, a small number of people who had traveled through high-risk regions were asked to track their temperatures, watch for symptoms and report their health to public health officials. Although experts emphasized that the risk to the public was extremely low, they were watching the outbreak closely because, similar to the Bundibugyo strain, existing vaccines and treatments also don’t work against the Sudan strain.

Prior to 2022, Ebola was a concern in the U.S. in 2014 and 2015. At that time, an Ebola outbreak in West Africa sickened more than 28,000 people. More than 11,000 of them died. That outbreak was the largest on record and involved the Zaire strain.

A man who had traveled from West Africa to Dallas, Texas, died of Ebola on Oct. 8, 2014. Two health care workers who treated the man contracted Ebola but survived. Altogether, 11 people were treated for Ebola in the U.S. during the 2014-2015 outbreak. Of the 11 (including the man from Dallas), two died. The others recovered.

Due to that Ebola outbreak, health experts across the U.S. developed plans and protocols to prepare for Ebola patients. They also learned how health workers could safely care for Ebola patients.

What is Ebola?

“Ebola is a hemorrhagic fever virus,” Barron said.

The virus is common in animals. It was first discovered in humans in 1976 near the Ebola River in what is now the Democratic Republic of Congo. That’s how the virus got its name.

According to the CDC, scientists do not know where the Ebola virus first came from, but it’s likely that it spread from a bat or a non-human primate to humans.

How does Ebola spread?

The virus spreads among people through direct contact with bodily fluids such as blood.

“This can be contact with saliva, blood, semen, emesis (from vomiting) or diarrhea,” Barron said.

Family members or health workers who care for people with Ebola can be infected if they are exposed to bodily fluids and then touch their eyes, nose or mouth. Ebola can also spread through sexual contact with an infected person.

The disease is most transmissible once a person becomes sick rather than during the incubation period.

What are the symptoms of Ebola?

Early-stage symptoms of Ebola include:

• Fever
• Headache
• Muscle pain
• Weakness
• Diarrhea
• Vomiting
• Stomach pain

Late-stage symptoms include:

• Unexplained bleeding or bruising

How long is the incubation period between exposure to Ebola and sickness?

Ebola has a much longer incubation period than some other infectious diseases, such as COVID-19 and the flu, Barron said.

“The average is about 7 to 10 days, but it can be up to 21 days. And so, there’s a really long incubation period. And that makes this challenging,” she said.

How transmissible is Ebola?

“Ebola is highly transmissible,” Barron said. “It’s more transmissible in what’s known as ‘the wet phase’ rather than ‘the dry phase.’ During the dry phase, people have fever, chills, body aches, that sort of thing. The wet phase is when people start having issues with bleeding, vomiting and diarrhea. That’s when they’re most infectious.”

Is the spread of Ebola similar to the way that COVID-19 or the flu spread from person to person?

No. The viruses that cause COVID-19 and the flu are respiratory viruses. They spreads through respiratory droplets. These droplets can stay suspended in the air or can contaminate objects and remain infectious for a short period of time. People can spread COVID-19 or the flu when they sneeze or cough. It is also possible for people who are asymptomatic to spread COVID-19 and the flu.

Ebola, on the other hand, spreads much less easily than COVID-19 or the flu. But it is also much deadlier, killing as many as half of the people who are infected.

How is this Ebola outbreak different from previous Ebola outbreaks?

Both the 2022 and 2014-2015 outbreaks were caused by different strains of Ebola.

“The current one is the Budibugyo strain, and the reason that matters is because the vaccine we currently have against Ebola doesn’t work for this particular strain,” Barron said.

Are there effective treatments for Ebola?

Yes, there are some treatments, but they are not effective against the Budibugyo or Sudan strains.

“The therapeutics we used for the 2014-2015 outbreak don’t work for this particular strain,” Barron said.

Are there additional strains of Ebola?

Yes. Researchers have thus far identified six strains of Ebola. They include the Zaire, Bundibugyo, Sudan, Taï Forest, Reston and Bombali strains, according to health experts at the World Health Organization.

There have been two previous outbreaks of the Bundibugyo strain: when it first appeared in Uganda in 2007-08 and then again in the DRC in 2012.

Are there vaccines for Ebola?

Yes. There is a vaccine for Ebola. It helps prevent the previous Zaire strain of Ebola that caused the outbreak in 2014 and 2015 but unfortunately does not work against the Bundibugyo strain.

The U.S. Food and Drug Administration approved the Ebola vaccine in 2019. It’s known as Ervebo or rVSV-ZEBOV.

There has been promising research for a vaccine that provides protection against the Bundibugyo Ebola infection, but currently, there is no approved treatment or vaccine.

How are health care workers in the U.S. preparing for Ebola?

Infectious disease experts in the U.S. always are prepared to fight Ebola and other worrisome diseases.

There are designated hospitals in each part of the country with special treatment units where medical providers can safely care for patients with Ebola.

At UCHealth’s clinics and hospitals, providers keep all patients safe by asking screening questions designed to flag potential concerns about Ebola.

“Everyone who enters our buildings, whether it’s through an emergency department or through a clinic, gets asked a question about travel. You’re asked, ‘Have you traveled outside the United States in the last 21 days?’”

For those who have not taken a recent trip, the screening ends.

Anyone who has traveled to countries of concern will be flagged for additional questions. Staff members know to take anyone at high risk for Ebola into a room where they can be isolated, and providers can put on personal protective equipment to examine the patient.

“If we have anyone with symptoms and a concerning travel history, then we activate our emergency preparedness plan,” Barron said. “That doesn’t mean people need to panic. It means we need to get a better, more detailed health history and ask, ‘What are your symptoms?’  ‘What were you doing in the DRC or Uganda?’ ‘Where, specifically, were you?’”

If hospital workers or other health officials flag any concerns with patients or recent travelers, experts can arrange for Ebola testing.

Again, the likelihood is much higher now that a person has a more common illness, Barron said. But she and other infectious disease specialists are bracing for an Ebola patient, just in case.