Ebola Virus Disease

Ebola Virus Disease

Ebola Virus Disease (EVD), formerly known as Ebola hemorrhagic fever, is a severe, often fatal illness in humans and nonhuman primates caused by the Ebola virus. The virus is part of the family Filoviridae, which also includes the Marburg virus.

History

The disease was first identified in 1976 in two simultaneous outbreaks, one in Nzara, Sudan, and the other in Yambuku, Democratic Republic of Congo, a village near the Ebola River, from which the disease takes its name.

Virology

Ebola virus is a filovirus, characterized by its filamentous structure. It is an RNA virus with a single-stranded, negative-sense genome. There are several species of the Ebola virus, including Zaire ebolavirus, Sudan ebolavirus, Taï Forest ebolavirus, Bundibugyo ebolavirus, and Reston ebolavirus.

Transmission

Ebola is transmitted to people from wild animals and spreads in the human population through human-to-human transmission. The virus is introduced into the human population through close contact with the blood, secretions, organs, or other bodily fluids of infected animals such as fruit bats, chimpanzees, gorillas, monkeys, forest antelope, and porcupines found ill or dead or in the rainforest.

Human-to-human transmission occurs via direct contact (through broken skin or mucous membranes) with the blood, secretions, organs, or other bodily fluids of infected people, and with surfaces and materials (e.g., bedding, clothing) contaminated with these fluids.

Symptoms

The incubation period, that is, the time interval from infection with the virus to onset of symptoms, is 2 to 21 days. Humans are not infectious until they develop symptoms. First symptoms are the sudden onset of fever fatigue, muscle pain, headache, and sore throat. This is followed by vomiting, diarrhea, rash, symptoms of impaired kidney and liver function, and in some cases, both internal and external bleeding (e.g., oozing from the gums, blood in the stools).

Diagnosis

Diagnosing EVD can be difficult. It is often confused with other infectious diseases such as malaria, typhoid fever, and meningitis. Laboratory tests used in diagnosis include:

• Antigen-capture enzyme-linked immunosorbent assay (ELISA)
• Polymerase chain reaction (PCR)
• Virus isolation by cell culture

Treatment

There is no proven treatment available for EVD. However, a range of potential treatments including blood products, immune therapies, and drug therapies are currently being evaluated. Supportive care - rehydration with oral or intravenous fluids - and treatment of specific symptoms improves survival.

Prevention

Good outbreak control relies on applying a package of interventions, namely case management, surveillance and contact tracing, a good laboratory service, safe burials, and social mobilization. Community engagement is key to successfully controlling outbreaks. Raising awareness of risk factors for Ebola infection and protective measures that individuals can take is an effective way to reduce human transmission.

Vaccines

An experimental Ebola vaccine, rVSV-ZEBOV, has been shown to be highly protective against the virus in a major trial in Guinea in 2015. The vaccine was used in the 2018-2020 Ebola outbreak in the Democratic Republic of Congo.

See Also

• Marburg virus disease
• Viral hemorrhagic fever
• Zoonosis

References

• World Health Organization. "Ebola virus disease." WHO, 2023.
• Centers for Disease Control and Prevention. "Ebola (Ebola Virus Disease)." CDC, 2023.