EBOLA VIRUS DISEASE (EVD), formerly known as Ebola hemorrhagic fever, is caused by a genus of viruses called Ebolavirus, which was first found in 1976 near the Ebola River in the Democratic Republic of Congo (known at the time as Zaire).1
Five subspecies of genus Ebolavirus have been identified. Four of the five cause illness in humans. Although no natural reservoir has been found, the most likely hosts for the virus are fruit bats of the Pteropodidae family.1,2
Transmission
The incubation period after exposure is typically 8 to 10 days, but can be as short as 2 days and as long as 21 days.1,2 Mortality is as high as 90%. Many people with EVD die within 2 weeks of disease onset.2
Most disease outbreaks occur in rural areas near tropical rainforests in the western and central regions of Africa.2 Primary transmission can occur from animal to human when a human eats or handles an infected animal.2,3 Disease transmission to humans has been documented from the handling of infected apes and monkeys, fruit bats, antelope, and porcupines.2
Secondary transmission of EVD from human to human can occur rapidly through direct contact with body fluids, including fluids from someone who died from EVD, or contact with contaminated objects that weren't properly sterilized.1,2 Healthcare workers caring for patients with EVD can become infected when infection control standards aren't followed meticulously.2
Because the disease is rapidly fatal, disease spread is somewhat self-limiting.4 However, men who survive EVD can transmit the virus through semen for up to 7 weeks after recovery.2
Could air travel trigger a pandemic?
A common worry is that someone with EVD could get on an airplane and carry this deadly disease around the world in the blink of an eye. Events in the news at the time of publication have indicated that air travel transmission of EVD is possible.5
Due to the severity and quick onset of EVD, an infected person is unlikely to be traveling by airplane. However, should this happen, certain people on the same flight should be monitored for infection: those sitting adjacent to the infected person, passengers and crew reporting direct contact with the person, and crew assigned to serve and clean the area where the person was sitting.6
Clinical manifestations
Initial signs and symptoms of EVD include abrupt onset of fever, headache, weakness, fatigue, pharyngitis, nonproductive cough, and myalgia, which can progress to abdominal pain, vomiting, diarrhea, dermatitis, and renal and hepatic dysfunction.1,3 As the disease progresses, the patient may experience both internal and external hemorrhage. Lab findings include leukopenia, thrombocytopenia, elevated serum aspartate aminotransferase and alanine aminotransferase levels, and proteinuria.1,2,3,7
Diagnosis
EVD is a diagnosis of exclusion, so other more common diseases should be considered first.1,2 Cholera, plague, meningitis, and other viral hemorrhagic fevers may cause initial clinical manifestations similar to those of EVD.2,4
An EVD diagnosis can be confirmed with various lab tests depending on the stage of disease. Within a few days of symptom onset, antibody-capture enzyme-linked immunosorbent assay, antigen detection tests, reverse transcriptase polymerase chain reaction (RT-PCR) assay, and virus isolation by cell culture can be used. Further into the course of the disease or after the patient recovers, immunoglobulin M and immunoglobulin G can be detected. After death, immunohistochemistry, PCR, and isolation of the virus can be performed.1
Treatment
No effective treatment for EVD exists at this time; currently available antiviral medications have no effect on Ebola virus.2,3 Supportive care for patients with EVD includes maintaining fluid and electrolyte balance via oral or I.V. hydration, supporting oxygenation and BP, correction of coagulopathy, and treating comorbidities such as a concurrent bacterial infection.1,2,4,7
Preventing transmission
In the hospital setting, healthcare workers caring for patients with suspected or confirmed EVD virus must use standard precautions. Personal protection equipment is mandatory to prevent exposure to the patient's blood and body fluids or direct contact with objects in the environment that may be contaminated. This includes gloves, gowns, and face protection such as a face shield or medical mask with goggles.2,8
People can best protect themselves from EVD by avoiding contact with infected body fluids. In areas where EVD is endemic, people are educated to avoid handling or eating raw meat from primates, thoroughly cook meat and other animal products before eating, and handle animals using gloves and other protective clothing.1,2
Secondary transmission can occur when families care for a sick relative or prepare a body for burial.1,9 Close physical contact should be avoided whenever possible; those caring for the patient must use protective clothing and follow strict infection control measures, including frequent hand hygiene.
Patients who die from EVD should be buried as soon as possible. Traditional burial rituals may need to be suspended to slow the spread of disease.4
Quarantine of infected individuals based on confirmed or suspected EVD is important to prevent the virus from spreading to others.9 However, cultural barriers influence the receptiveness of vulnerable populations to these preventive measures. People in small rural villages may reject medical advice in favor of culturally accepted folk remedies intended to rid their land of the illness.4 Further research is needed to help protect these people and limit EVD outbreaks.
Is vaccination an option?
Currently, no effective vaccine is available to combat EVD. The immune response to Ebola virus is complex, which complicates vaccine development. However, the risk that Ebola virus could be used for bioterrorism may prompt more research to create a vaccine that would protect against all strains of Ebola virus and similar lethal viruses.3
For the most up-to-date information about EVD outbreaks, visit http://www.afro.who.int/en/clusters-a-programmes/dpc/epidemic-a-pandemic-alert-a.
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