In 1976, an almost simultaneous outbreak of an acute infectious disease characterized by fever, hemorrhage, and damage to multiple organs occurred in southern Sudan and northern Democratic Republic of the Congo (formerly Zaire). This disease can be transmitted between humans and primates.

In the past 40 years, there have been 24 outbreaks worldwide, resulting in nearly 2,000 infections and over 1,300 deaths. Various countries have reported a case fatality rate ranging from 53% to 88%.

WHO medical experts isolated a new filovirus from patient specimens, which was similar in morphology to the Marburg virus but had different immune characteristics. This virus was later named after the Ebola River in the Democratic Republic of the Congo, the focus of the epidemic, and called Ebola virus (EBV). The disease caused by it was named Ebola hemorrhagic fever (EBHF). The World Health Organization classifies Ebola as "Biosafety Level 4 (BSL-4)," indicating it is extremely harmful to humans. In contrast, AIDS is classified as Level 2, and SARS as Level 3.

Natural Reservoir

Studies have shown that EVD outbreaks have multiple origins and may have multiple hosts. Scientists believe that chimpanzees, gorillas, and monkeys are all natural hosts for the Ebola virus, while bats are considered intermediate hosts capable of spreading the virus. In Guinea, bats were identified as responsible for the Ebola outbreak that began in March 2014.

In addition to natural hosts, recent studies have confirmed that pigs and dogs are the only domestic animals known to be infected with the Ebola virus.

Types of Ebola Virus

1. Zaire ebolavirus (EBOV)

2. Sudan ebolavirus (SUDV)

3. Tai Forest ebolavirus (TAFV)

4. Bundibugyo ebolavirus (BDBV)

5. Reston ebolavirus (RESTV)

Transmission

Ebola is primarily transmitted through direct or indirect contact with the blood, body fluids, secretions, and excretions of infected individuals via broken skin or mucous membranes. The virus is most contagious in the blood, feces, and vomit of patients. Unlike COVID-19, Ebola is not typically spread through airborne aerosols and small droplets.

Ebola is highly contagious, and patients can remain infectious even after 7 weeks of recovery. According to the World Health Organization, men who have had Ebola can still transmit the disease to their sexual partners through semen during this period of recovery.

Symptoms

The Ebola virus has a diameter of only 80 nanometers, yet its impact on the human body is devastating. Upon infection, patients experience internal bleeding followed by bleeding from all seven orifices. They often vomit necrotic tissue from their internal organs and ultimately succumb to extensive internal bleeding, brain damage, and other complications. As described by medical professionals, those infected with Ebola can appear to "melt" due to the severe effects it has on their bodies.

Symptoms of systemic poisoning, such as high fever, headache, sore throat, weakness, and muscle pain, typically manifest within 1-2 days of Ebola infection. These initial symptoms are often followed by severe vomiting, abdominal pain, and diarrhea.

Coagulopathy and thrombocytopenia can develop within 24 to 48 hours of Ebola infection, leading to bleeding from the nose or mouth and the formation of hemorrhagic skin blisters.

Renal failure can occur within 3-5 days of Ebola infection, progressing to multi-organ failure and disseminated intravascular coagulation.

In addition, the Ebola virus can invade the human brain, leading many individuals with Ebola hemorrhagic fever to experience symptoms such as seizures, tremors, or general neurological disturbances before succumbing to the disease.

Diagnosis and Treatment

- Diagnosis

Diagnosing Ebola Virus Disease (EVD) early in its course can be challenging, as initial symptoms may resemble those of other infectious diseases like influenza or malaria. Therefore, obtaining a detailed travel and exposure history is crucial to assess whether the illness could be attributed to EVD or other travel-related infections. Test results can take several days to confirm, and sometimes tests may need to be repeated to ensure accuracy.

- Treatment

After years of trials, validations, tests, and improvements, the world's first Ebola vaccine, Ervebo, was approved by the European Commission and the United States FDA by the end of 2019. Over 300,000 doses have been administered in heavily affected regions like Guinea and the Democratic Republic of the Congo, utilizing a ring vaccination strategy where all individuals exposed to confirmed Ebola cases are vaccinated.

In addition to the approved Ebola vaccine Ervebo, scientists finalized two drugs in August 2019 that can significantly reduce mortality from Ebola virus disease: mAb114 and REGN-EB3. These antibody therapies have shown to improve the survival rate of patients to 70%.