Ebola Virus Disease

Ebola virus disease is a severe, frequently fatal viral hemorrhagic fever caused by Ebolavirus species (filoviruses), with periodic outbreaks occurring predominantly in parts of Central and West Africa.

Case fatality rates have varied considerably between outbreaks and species, historically ranging from roughly 25% to as high as 90%, influenced by the specific viral species, quality of supportive care available, and speed of outbreak response.

Transmission occurs through direct contact with the blood, body fluids, or secretions of an infected, symptomatic person (or their remains, notably relevant to traditional burial practices involving direct contact with the deceased, an important factor in some outbreak transmission chains), or, less commonly for human to human spread, through contact with infected animals, with fruit bats considered a likely natural reservoir.

Illness typically begins abruptly after an incubation period of roughly 2 to 21 days, and progresses through recognizable phases, though the pace and severity vary between patients.

• Early phase: sudden onset fever, severe headache, myalgia, sore throat, and profound fatigue, a non-specific presentation that can be difficult to distinguish from many other causes of febrile illness in an endemic region without a clear epidemiological exposure link.
• Gastrointestinal phase: severe vomiting and diarrhea, often profuse, contributing to significant fluid and electrolyte losses that are, in many outbreaks, a major driver of mortality if not adequately managed, arguably more so than the hemorrhagic manifestations themselves despite the disease's name and reputation.
• Later phase: in a proportion of patients, bleeding manifestations develop, including petechiae, mucosal bleeding, and, in severe cases, more significant internal or external hemorrhage, alongside progression to multi-organ dysfunction, shock, and, in fatal cases, death typically occurring around 6 to 16 days after symptom onset.
• Survivors can experience a prolonged convalescent phase with persistent symptoms (fatigue, joint pain, ocular complications), and the virus can persist in certain immune privileged body sites (notably semen) for an extended period after clinical recovery, with implications for sexual transmission risk and survivor counseling.

• RT-PCR testing of blood is the standard diagnostic method, with high sensitivity once the patient is symptomatic and viremic.
• Diagnostic testing for suspected Ebola requires specific biosafety precautions and should only be performed in appropriately equipped and trained facilities, given the high risk of the pathogen and the need to protect laboratory personnel.
• Given the non-specific early presentation, a detailed epidemiological exposure history is essential in any patient presenting with a compatible febrile illness in or recently returned from an area with a known or suspected outbreak, since this exposure history, more than clinical features alone, is what should trigger the specific isolation and testing pathway.
• Routine bloods (FBC, U&E, LFTs, coagulation profile) support assessment of severity and guide supportive management, though should only be performed with appropriate precautions given the infection risk from handling the specimens.

Differentials include malaria (which must always be actively tested for and, if positive, does not exclude concurrent Ebola given the overlapping endemic geography), typhoid fever, and other viral hemorrhagic fevers (Marburg, Lassa fever, Rift Valley fever).

Any patient with a compatible clinical presentation and a relevant epidemiological exposure history requires immediate isolation and urgent notification of public health and infection control authorities, before extensive further assessment, given the risk of onward transmission to healthcare workers and other patients if appropriate precautions are not instituted promptly.

• Supportive care is the foundation of management, and aggressive, well delivered supportive care has been shown to substantially improve survival: meticulous fluid and electrolyte replacement (given the often severe losses from vomiting and diarrhea), management of shock, correction of coagulopathy and management of bleeding, and treatment of any secondary bacterial infection.
• Specific antiviral treatment is now available for Ebola caused by the Zaire species, with monoclonal antibody therapies (including regimens such as REGN-EB3 and mAb114) having demonstrated survival benefit in clinical trials when given early in the illness course, representing a genuine advance from the purely supportive approach of earlier outbreaks.
• Strict infection prevention and control measures are essential throughout care, including appropriate personal protective equipment for all healthcare workers, safe handling of body fluids and waste, and safe and dignified burial practices for those who die of the disease, given the very high transmission risk associated with direct contact with a deceased patient's body.
• Ebola vaccines are now available and have been used effectively for outbreak control, both for at risk contacts of confirmed cases (ring vaccination strategies) and for frontline healthcare and response workers, representing an important addition to the outbreak response toolkit alongside case isolation, contact tracing, and supportive care.
• Survivor follow up and support addresses the range of persistent post recovery symptoms and complications, alongside specific counseling regarding the period of viral persistence in certain body fluids and its implications.

Referral: this is a public health emergency requiring immediate notification and coordination with public health and infectious disease authorities; specialist high consequence infectious disease units should be engaged as early as possible for confirmed or strongly suspected cases.