Previous Ebola outbreaks have seen fatality rates as high as 90%. The current epidemic, primarily across Gambia, Sierra Leone, and Liberia, has seen 729 deaths out of more than 1353 confirmed infections, which equals about a 53% mortality rate to date.
Ebola virus is a member of the Filoviridae family. First isolated in 1976, 5 subtypes of Ebola virus are now recognized, of which 4 are pathogenic to humans. The Reston subtype infects only primates. The most deadly form is the Zaire subtype, with the natural reservoir for the virus believed to be the fruit bat. The virus has also been found in porcupines, primates, and wild antelope.
Ebola virus incubates in infected humans for 2-21 days, with the majority of patients becoming symptomatic after 8-9 days. Once infected, patients can experience severe symptoms within 1-2 days.
Symptoms of Ebola include:
- Sudden fever, often as high as 103º-105º F;
- Intense weakness, sore throat, and headache; and
- Profuse vomiting and diarrhea (occurs 1-2 days after the aforementioned symptoms).
More severe symptoms, such as the development of coagulopathy with thrombocytopenia, can develop in as soon as 24-48 hours, leading to bleeding from the nasal or oral cavities, along with hemorrhagic skin blisters. The development of renal failure, leading to multisystem organ failure along with disseminated intravascular coagulation, can then rapidly ensue over 3-5 days, along with significant volume loss.
Patients who develop a fulminant course often die within 8-9 days. Those who survive beyond 2 weeks have a better prognosis for survival.
The Difficulties of Ebola Diagnoses
One of the difficulties encountered in identifying Ebola virus is that in the early days of the disease, the symptoms may be similar to those of other types of infectious diseases, such as malaria, Lassa fever, typhoid, cholera, and even meningitis. Only after 3-5 days (or even later in the course of the disease) might the hemorrhagic blisters — along with internal hemorrhage, the hallmark of the illness — become evident.
Although Ebola is a highly contagious virus, it is not airborne and not spread by droplets, such as how measles and influenza are transmitted. You cannot acquire Ebola virus if another person coughs or sneezes close to you, and it is not spread by casual contact. Rather, it is acquired by direct contact with infected secretions such as vomit, diarrhea, and blood primarily. It may also be spread by direct contact with saliva, sweat, and tears. Other means of transmission include contact of secretions with a skin opening or healing wound, or if a person contacts secretions and touches his or her eyes, nose, or mouth.
It is important to remember that only patients who are symptomatic are contagious and can then transmit the virus to others through their secretions. Those who have contracted the disease are primarily healthcare workers caring for patients, as well as family members who have had close contact with infected patients. Another method of infection has involved family members who handle corpses at the time of burial, along with those who eat fruit bats, antelope, or other animals potentially infected with the virus.
Studies indicate that the virus is in much higher concentration in vomit, blood, and diarrhea compared with saliva, sweat, and tears, making disinfection of public areas such as restrooms imperative in order to contain the virus.
The actual risk to citizens living and working in the United States is quite low, and the public should be well aware that emergency departments (EDs) and critical care units in the United States are well equipped and prepared in the event that a patient with a recent travel history from West Africa, along with flu-like and gastrointestinal symptoms, presents to the hospital.
As the ED is often the proverbial “front door” to the hospital, universal precautions, along with a protocol to quarantine and isolate such patients, is now a top priority for all EDs. Such a plan requires healthcare providers to wear personal protective equipment, including eyewear or goggles, facemask, gloves, and a gown.
Effective decontamination methods for the virus include steam sterilization, chemical sterilization, incineration, and gaseous methods.
Limited Treatments for Ebola
At this time, only supportive care is available (intravenous fluids; blood and platelet transfusions), although upcoming human vaccine trials may be promising.
The National Institutes of Health will begin a human vaccine trial in September 2014, according to recent statements from Dr. Anthony Fauci, Director of the National Institute of Allergy and Infectious Diseases (NIAID). Previous attempts at a human vaccine in the early 2000s were not successful
The current vaccine, developed by the NIAID Vaccine Research Center, contains no infectious Ebola virus material. It is actually a chimpanzee adenovirus vector vaccine that has incorporated 2 Ebola virus genes. Adenovirus vectors are useful delivery models as vaccines because the virus can be easily manipulated. As a nonreplicating viral vector, the vaccine works by entering a cell and delivering the new genetic material. The new genes that are inserted cause a protein to become expressed, which in turn produces an immune response in the body. According to NIAID, the vaccine has shown early promise in a primate model.
Another approach to help infected patients involves transfusing blood or plasma from those patients who have recently recovered from Ebola virus infection. This approach is based on the premise that the plasma from recovered patients contains life-saving antibodies. This is an experimental treatment that has been used, according to recent reports during this epidemic, although results of such treatment have not been formally reported.
Use of an experimental compound, referred to as BCX4430, was reported in the journal Nature in April 2014. The compound, an RNA-dependent RNA polymerase inhibitor, has proven successful in a nonhuman primate model, whereby postexposure prophylaxis to BCX4430 prevented death in 17 of 18 macaques studied. No human trials have yet been reported.