5 things to know about the Ebola outbreak

Michele Barry, director of the Stanford Center for Innovation in Global Health, explains how this strain differs, why public risk outside the DRC remains low, and what a global response requires.

An Ebola outbreak in the Democratic Republic of the Congo (DRC) has caused alarm and raised questions about the serious viral illness this week. While officials first declared the outbreak on May 15, the virus likely had been sickening people for weeks before that. As a result, more than 130 deaths and more than 500 infections were suspected as of May 20.

The World Health Organization (WHO) on Sunday declared a public health emergency of international concern to mobilize an international response and help prevent the disease from spreading between countries.

In light of the headlines and a U.S. ban on travelers from affected countries, you might wonder how worried you should be.

While the outbreak is a serious concern in the DRC and nearby countries, the risk to people in the U.S. and most other regions of the world is extremely low, says Michele Barry, MD, senior associate dean of global health and director of the Stanford Center for Innovation in Global Health.

“Widespread transmission is very unlikely with Ebola,” she said. “However, a timely and collaborative global response is vital to support the DRC and its neighbors in tracking and containing this outbreak and saving lives.”

Barry has experience responding to Ebola in Uganda and Liberia and has written about how to strengthen health systems for more effective responses. She is among the few doctors to have cared for someone with a hemorrhagic virus in the U.S.

Here’s what she wants you to know.

1. Ebola is much less contagious than COVID-19 or measles, and public risk outside of the affected region is very low.

“Ebola is extremely infectious, but not easily spread,” Barry emphasizes. It is infectious because exposure to a very small amount of the virus can trigger a potentially fatal infection.

However, Ebola is transmitted via direct exposure to bodily fluids, making the risk to the general public much lower than with airborne diseases such as COVID-19 and measles. Typically, the disease spreads through direct contact with broken skin or unprotected mucous membranes.

Handling the dead without adequate protective gear is the strongest risk factor, Barry adds. Health care workers can be at risk for airborne infection when medical procedures create aerosol particles containing the virus.

“While the risk of a pandemic is very low given the way the virus spreads, the impact in the DRC and nearby countries could be devastating,” Barry said. “Countries like the U.S. should take a universal approach to quarantine and travel bans, as viruses don’t respect passports. Policies should be backed by scientific evidence and carefully coordinated with other countries to ensure that they are effective.”

2. The virus causing this outbreak presents unique challenges.

There are six known virus species linked to Ebola, but only three cause the largest outbreaks: Zaire virus, Sudan virus, and Bundibugyo virus, the latter of which is behind the current epidemic.

Bundibugyo virus is the least common, causing only two outbreaks before this one. Not all Ebola diagnostic tests can detect Bundibugyo, which is one of the reasons this outbreak spread undetected for so long.

Bundibugyo virus presents with clinical features similar to other Ebola viruses, such as fever and weakness. However, it also has distinguishing features, Barry said. Non-bloody diarrhea and headache are seen as the first symptoms more than 80% of the time. Hemorrhagic symptoms are less common first symptoms, appearing about 25% of the time.

3. Ebola vaccines and therapies exist—but not for this strain.

Barry noted that excellent vaccines exist to prevent Ebola, with some studies showing over 90% efficacy, but they are specifically designed to prevent the Ebola-Zaire form of the virus. Likewise, therapies such as monoclonal antibodies have been developed but are untested for this strain.

Unfortunately, there are no approved vaccines or therapies to treat or prevent this version of Ebola. WHO scientists are already moving to begin trials for experimental treatments and possibly vaccines.

In the meantime, prevention is critical, including contact tracing and good personal protective equipment for health care workers, along with supportive care for patients, Barry emphasized. She added that burials should be carefully supervised to ensure that no exposures occur, and patients with Ebola should be cared for in designated biocontainment centers.

4. Survival rates vary widely based on treatment access.

Bundibugyo’s fatality rate is lower than the highly fatal Ebola-Zaire form, estimated to be between 30–50% in prior outbreaks, Barry said.

“Importantly, Ebola’s fatality rate can be much lower with access to high-level intensive care units,” she added.

“During the 2014-2016 West Africa outbreak, we saw a stark difference in mortality rates for the few patients who were cared for in the U.S.,” Barry said. “They fared much better than patients in Sierra Leone, Guinea, and Liberia.”

A study found that patients treated for Ebola in the U.S. and Europe during the 2014-15 outbreak had an 18.5% mortality rate. In the DRC, mortality has remained over 50% in recent outbreaks.

“Combating Ebola in conflict settings such as in the DRC is challenging because of weakened health care systems and difficult contact tracing,” Barry added.

5. Ebola virus underscores our global interconnectedness.

Barry emphasizes that Ebola is a prime example of the interconnectedness of humans and their environment. Epidemics are generally thought to begin when a person is exposed through contact with an infected animal. Although the true animal reservoir of Ebola is not known, fruit bats are strongly suspected.

“Great apes like us are severely affected by Ebola, and interestingly, gorilla or chimpanzee die-offs often occur before or during human outbreaks,” Barry said.

The current epidemic is happening in a region affected by gold mining and deforestation, and research has shown that deforestation increases a region’s risk for outbreaks as it pushes animals into closer contact with people.

At the same time, conflict in the DRC has weakened its health care system and displaced large numbers of people, all of which present significant challenges to containing this outbreak, Barry noted.

“With increasing deforestation and other environmental pressures, we’re likely to see more and more outbreaks caused by animal-human interaction,” Barry said. “It’s more important than ever to collaborate across borders and strengthen health care and disease surveillance systems. Through international collaboration, we can swiftly detect and respond to outbreaks.”

Who’s behind this story?

Sadie Harley

BSc Life Sciences & Ecology. Microbiology lab background with pharmaceutical news experience in oil, gas, and renewable industries.

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Andrew Zinin

Master’s in physics with research experience. Long-time science news enthusiast. Plays key role in Science X’s editorial success.

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