Ebola: Inside the Deadliest Outbreaks

What is Ebola?

Ebola virus disease (EVD), formerly known as Ebola hemorrhagic fever, is a severe, often fatal illness in humans caused by the Ebola virus.[5] The virus belongs to the family Filoviridae, named for their distinctive filament-like shape under electron microscopy.

Ebola spreads through direct contact with bodily fluids of infected people or animals, or with contaminated surfaces. It does not spread through air like influenza. Healthcare workers and family caregivers are at highest risk.

Discovery and Natural Reservoir

Ebola was first identified in 1976 during simultaneous outbreaks in what is now the Democratic Republic of Congo and South Sudan. The disease was named after the Ebola River in Congo, near where the first outbreak occurred.

Fruit bats are believed to be the natural reservoir of Ebola virus. They carry the virus without becoming ill and can transmit it to other animals or humans. Outbreaks often begin when humans come into contact with infected wildlife, such as hunting or butchering bush meat.

Clinical Progression

Ebola has an incubation period of 2-21 days (average 8-10 days). The disease progresses through distinct phases:

1. Early phase (days 1-3): Sudden onset of fever, fatigue, muscle pain, headache, sore throat
2. GI phase (days 3-5): Vomiting, diarrhea, abdominal pain (massive fluid loss)
3. Hemorrhagic phase (days 5-7): Internal and external bleeding, rash, organ failure
4. Resolution: Death or gradual recovery (survivors may have prolonged virus persistence)

Despite its reputation for causing bleeding, hemorrhage is not universal. The primary causes of death are shock from massive fluid loss and multi-organ failure.

The 2014-2016 West Africa Epidemic

Previous Ebola outbreaks were contained to remote villages in Central Africa, rarely exceeding a few hundred cases. The 2014-2016 outbreak shattered all precedents:

• 28,616 cases and 11,325 deaths across Guinea, Liberia, and Sierra Leone[1]
• First urban Ebola outbreak
• Cases exported to 7 countries including the US and Europe
• Overwhelmed health systems already weakened by civil wars
• Sparked international emergency response

The epidemic revealed catastrophic gaps in global health security. The initial response was slow, and the world watched as the virus spread unchecked for months. It took unprecedented international mobilization, including military involvement, to finally contain the outbreak.

Treatment

For decades, Ebola treatment was purely supportive: intensive fluid replacement, electrolyte management, and treating secondary infections. Mortality remained devastatingly high.

This changed with the development of monoclonal antibody treatments:

• Inmazeb (REGN-EB3): Combination of three monoclonal antibodies; FDA approved 2020
• Ebanga (mAb114): Single monoclonal antibody; FDA approved 2020

In a landmark clinical trial during the 2018-2020 DRC outbreak, these treatments reduced mortality significantly. Patients who received treatment early had survival rates of approximately 90%.[3]

Vaccines

The first Ebola vaccine, rVSV-ZEBOV (Ervebo), was approved in 2019. It uses a modified vesicular stomatitis virus to deliver Ebola glycoprotein, generating immune response without causing disease.

The vaccine proved highly effective during the 2018-2020 DRC outbreak, protecting vaccinated individuals and helping contain spread through ring vaccination of contacts.[4]

"Ebola taught us that in our interconnected world, an outbreak anywhere is a threat everywhere. The next pandemic is not a matter of if, but when."

Lessons Learned

The Ebola outbreaks fundamentally changed global health security:

• WHO reform: Health Emergencies Programme created after criticism of slow response
• Vaccine development: Demonstrated that vaccines can be developed and deployed rapidly
• Treatment advances: Showed clinical trials can be conducted during epidemics
• Health system strengthening: Highlighted need for resilient healthcare infrastructure
• Community engagement: Emphasized importance of trust and cultural sensitivity

Ebola continues to cause periodic outbreaks in Central Africa. As of 2024, there have been 16 known outbreaks. Each one tests the lessons learned and the systems put in place. The hope is that with vaccines, treatments, and better preparedness, the devastation of 2014-2016 will never be repeated.