Etiology
The pathogenesis of Ebola is not clear but, once in the human body, the virus replicates in a variety of cell types—including dendritic cells, monocytes, and macrophages—with consequences including coagulation abnormalities, vascular instability, a robust inflammatory response, and extensive focal necrosis that tends to be most severe in the liver, spleen, lymph nodes, kidney, lung, and gonads. Death typically occurs secondary to a septic shock-like syndrome within 10 days of symptom onset; patients who survive ≥ 2 weeks often recover. The incubation period varies from 2–21 days (but is typically 8–10 days), during which time the infected patient is not contagious; the patient is not considered contagious until the onset of symptoms (typically, fever). Early symptoms are nonspecific and can be confused with those of other diseases, including malaria, dengue, and typhoid fever.
Pathophysiological Process and Clinical Manifestations
The Ebola virus is an enveloped single-stranded negative sense RNA virus member of the family Filoviridae, genus Ebolavirus, and order Mononegavirales. Five Ebola strains have been identified: Zaire Ebolavirus, Bundibugyo Ebolavirus, Taï Forest Ebolavirus, Sudan Ebolavirus, and Reston Ebolavirus (Borchardt, 2015). The current outbreak is most closely related to the Zaire strain, at about 97% homology. The Zaire strain has the highest reported overall mortality, 60% to 88% for previous outbreaks; mortality from the current epidemic strain is estimated at 60% (Borchardt, 2015). The current virus strain likely diverged from a common central African Ebola virus ancestor about 2004, and probably arose from a single natural reservoir transmission, followed by human-to-human transmission with the outbreak.7 The natural reservoir has not been clearly established, but fruit bats from regions of previous Ebola outbreaks have tested positive for Ebola virus, suggesting zoonotic transmission from a bat reservoir.8 The initial human infection is thought to have occurred following contact with an Ebola virus-infected animal, perhaps through the ingestion of contaminated nonhuman primate bush meat or from direct exposure to infected animal blood or fluids (Borchardt, 2015).
Human-to-human transmission occurs through direct exposure to an infected individual’s body fluids, including blood, urine, feces, saliva, vomit, or from objects contaminated with infected fluids (such as needles and syringes). Patients most at risk for contracting Ebola are those from active endemic areas; those who have traveled to these areas within the last 21 days; and those who have had direct percutaneous (needlestick) or mucous membrane exposure to Ebola-infected blood or body fluids, direct skin contact with infected blood or fluids, or direct contact with a dead body without wearing appropriate personal protective equipment (Borchardt, 2015). High-risk patients include family members and friends who may have come in contact with infected fluids of symptomatic patients and healthcare workers directly exposed to infected blood or body fluids because they were not wearing appropriate personal protective equipment or practicing standard biosafety precautions (Borchardt, 2015).
In the initial disease presentation, symptoms of acute-onset fever (temperature greater than 38.6° C [101.5° F]), chills, myalgia, and malaise can be mistaken for other tropical diseases, such as malaria or dengue fever. Ebola can progress to flu-like symptoms with cough, runny nose, and shortness of breath; however, the disease is not airborne. The more prominent symptoms are of a progressive gastrointestinal nature: nausea, vomiting, diarrhea, and abdominal pain that result in intravascular volume depletion, hypoperfusion, shock, profound electrolyte abnormalities, metabolic acidosis, and marked hepatocellular injury with aminotransaminase elevation. Other laboratory findings include anemia, leukopenia, thrombocytopenia, and elevated prothrombin and partial thromboplastin times. Lymphopenia is a marker of poor prognosis.
Diagnosis
Ebola testing to confirm diagnosis is only effective after the viral load has reached a level to where symptoms are present. Although the viral load may not be detectable until the patient has been symptomatic for several days, laboratory tests (white blood cell count, liver function, amylase, and coagulation studies) associated with affected organs may show changes (Richardson, 2015). Therefore, supportive treatment of symptoms usually starts before confirmation of the disease.
No vaccine has been proven to prevent Ebola and no antiviral medicine effectively treats the disease. Treatment is limited to basic symptomatic control, administering IV fluids and electrolyte replacement, maintaining oxygen saturation and BP, and treating complicating infections as they arise. A patient’s immune status determines ability to recover from Ebola. Patients who recover develop neutralizing antibodies to Ebola virus that are detectable for up to 10 years, suggesting a potential treatment role for passive immunity. The WHO has approved the use of serum from convalescing patients to treat new patients with acute Ebola. This decision came after the WHO heard testimony about a 1995 Ebola outbreak during which blood products from five convalescing patients were used to treat eight infected patients, and only one patient died.
Conclusion
In time when worldwide travel is more acceptable thanks in part to technological advancements that have permitted healthcare workers to travel to distant lands and assist in providing state of-the-art care to those who are impoverished. As healthcare personnel educate many who are not up to date on basic lifesaving measures, they simultaneously become more susceptible to foreign pathogens such as Ebola Virus Disease.
Ebola Virus Disease (EVD) is a rare and deadly disease in people and nonhuman primates. The viruses that cause EVD are located in sub-Saharan Africa. People can get EVD through direct contact with an infected animal (bat or nonhuman primate) or a sick or dead person infected with Ebola virus (Center of Disease and Control and Prevention [CDC], 2018). The Ebola outbreak is far from over, so PAs, especially first responders in emergency or urgent care facilities, must remain vigilant and informed of the ongoing developments of this epidemic. (Borchardt, 2015).
References
- Bodine, E.N., Cook, C., & Shorten, M. (2018). The potential impact of a prophylactic vaccine for Ebola in Sierra Leone. Mathematical Biosciences And Engineering: MBE, 15(2), 337-359. https://doi-org.chamberlainuniversity.idm.oclc.org/10.3934/mbe.2018015
- Borchardt, R. (2015). The Ebola virus epidemic: Preparation, not panic. Journal of the American Academy of Physician Assistants, 28(2), 48-50. doi:10.1097/01.JAA.0000459821.32532.10
- Richardson, K. (2015). Ebola virus disease. Advanced Emergency Nursing Journal, 37(2), 102-115. doi:10.1097/TME.0000000000000063
