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A Study on One of the Worst Biological Threats of Last Century: Ebola Virus Outbreak

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Abstract

Ebola Virus Disease (EVD) is a zoonosis disease that has caused a massive outbreak in 2014, killing over 11,000 people with over 28,000 reported cases worldwide. Now that Ebola is considered a Category A biological threat, more research has been done to examine the epidemiology behind the disease and ultimately acquire new knowledge about EDV and ways to prevent future spread of the infection. This paper will outline information from peer reviewed articles currently available on EVD and how it is transmitted and prevented in communities where the virus is prevalent. Ebola Virus Disease is first examined through an epidemiological triad model and the mode of transmission is discussed. The prevalence/incidence of Ebola in Sierra Leone, Liberia, and the United States is compared and whether or not EVD is a notifiable disease is determined. A description of the typical course of illness for an Ebola victim is outlined as well as diagnostic studies, availability of vaccines, and treatment options. This paper also contains a fictitious scenario of an Ebola cluster to describe how the virus may spread and cause an outbreak and a prevention plan is also developed and discussed.

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Ebola Virus Disease

The Ebola outbreak of 2014 is the world’s largest outbreak in history with over 28,000 reported cases and over 11,000 deaths worldwide (World Health Organization [WHO], 2015, “Ebola Situation Report”). Ebola has also sparked a massive amount of fear across the world; a reported story recounted an incidence in a Spanish airport where a man was left to die with no medical attention for nearly an hour due to fear of infection (Casey, 2015). Up until now, there has been very little known about the tropical disease. Ebola is now considered a Category A biological threat and much more research has been done. This report is a literature review on information about Ebola and how to prevent and manage it. As healthcare workers, it is our duty to be fully informed about Ebola and able to provide adequate care and reassurance to communities and individuals affected by the disease in order to prevent the spread (Rio, Mehta, Lyon, & Guarner, 2014).

Epidemiologic Triad Model (Agent, Host, Environmental Factors)

The Ebola Virus Disease (EVD) is a zoonosis disease which is an infectious disease of an animal that is transmitted to humans. The agent of EVD are viruses of the Filoviridae family, comprised of two types of RNA viruses: Marburgvirus and Ebolavirus. Five species of the Ebola virus has been identified and named according to their geographical location: Ebola (EBOV,) Sudan (SUDV), Tai Forest (TAFV), Bundibugyo (BDBV), and Reston (RESTV) (Bulton, 2015).

Fruit bats are believed to be the natural reservoir host for EBOV, although it has yet to be confirmed (Rio et al., 2014). The fruit bats, which are believed to be of the Zaire species, not only affect humans, but have also been shown to infect other animals such as gorillas, monkeys, apes, and porcupines. (Bulton, 2015). Possible triggers that increase viral transmission include concurrent infection with other pathogens, pregnancy, stress, or changes in sources for food. Humans and animals that have a high mortality rate to EVD are end hosts, not reservoir host species. The incidence of EVD is higher in adults than children, although this can because of the fact that adults come into contact with infectious patients more often than children do. Also, there is no difference in susceptibility between men and women. The high incidences in Africans is probably due to their geographical location and there is no evidence that ethnicity is a factor in host vulnerability (Casey, 2015)

Since the virus is enveloped, it requires a continuously moist environment (EBOV is a tropical virus), and will not survive when exposed to dry conditions. There is an increase in spread of the virus in areas with “overcrowded living conditions, poor public infrastructure, poorly funded health services, and low levels of health and scientific literacy” (Casey, 2015). These environmental factors have enabled EBOV to become a much more virulent pathogen.

Chain of Infection (Mode of Transmission)

The way in which the Ebola virus first presents itself in a human at the beginning of an outbreak is unknown because the natural reservoir host of the virus has yet to be identified. However, scientist suspect that the victim first becomes infected through contact with an infected animal, such as a primate or a fruit bat; this is known as a “spillover event” (Centers for Disease Control and Prevention [CDC], 2015, “Transmission”). EVD is transmitted through mucous membranes or broken skin that comes into direct contact with any bodily fluids such as secretions, blood, or organs from an infected person, object, or animal (Boulton, 2015). This includes: Infected primates or fruit bats, objects such as needles or syringes that have been contaminated with infected fluid, blood or body fluids (fees, vomit, breast milk, urine, saliva, and sweat). Ebola is not an airborne infection, and cannot be spread though water or food. There is currently no evidence that the virus can be transmitted by a vector such as mosquitoes or insects. (Rio et al., 2014).

The Ebola virus has also been found in the semen of some men who have recovered from Ebola, therefore, it is possible for the Ebola virus to be sexually transmitted (through oral, vaginal, or anal sex). According to published reports of previous EVD outbreaks, it has been demonstrated that survivors of EVD can continue to harbor the virus in immunologically privileged sites in their body (certain sites of the human body that are able to tolerate the introduction of antigens without evoking an immune response) for a certain amount of time after recovery. The virus has been isolated from semen for as long as 82 days after the initial onset of symptoms. Viral RNA has also been detected in semen for up to 101 days after the onset of symptoms (Christie et al, 2015). However, the time it takes for the virus to be fully eliminated from the semen is different for each man. Evidence of the virus being spread through sexual contact with vaginal fluids from a woman who has recovered from Ebola has yet to be proven (CDC, 2015, “Transmission”).

Since infection occurs through direct contact with infected bodily fluids or through parenteral injection, most cases occur in individuals providing direct care to patients such as healthcare workers or family members of the patients. Transmission to household members is usually due to exposure at funerals and medical practices. An increase in transmissions occurs in medical settings and facilities, which accounts for approximately 25% of cases that occur among healthcare workers (Rio et al., 2014).

Incidence / Prevalence

According to the World Health Organization, the largest outbreak of Ebola occurred in Sierra Leone with 14,001 reported cases with a total of 3,955 deaths since the March 2014 outbreak (2015). This makes it the largest outbreak area in the world and the largest outbreak in history. Compared to Sierra Leone, Liberia, the second largest outbreak area, has reported 14,001 cases with 4,808 deaths since March 2014. These numbers are greatly unproprotional to the incidence in the U.S., which only had four reported cases and one death and of the four reported cases, many of them were coming in from Africa. The incidence gap between Sierra Leon and Liberia as compared to the U.S. is most likely due to economic barriers in West Africa where access to basic healthcare equipment is limited and tertiary care facilities are sparse (WHO, 2015, “Ebola Situation Report”).

Is The Disease Reportable?

Ebola virus disease is reportable to the National Notifiable Disease Surveillance System (NNDSS) in all U.S. states and other territories (CDC, 2014, “Case Definition”). Anyone suspected of contracting Ebola must be monitored. Person Under Investigation (PUI) is someone that meets two criteria: “(1) Elevated body temperature or subjective fever or symptoms, including severe headache, fatigue, muscle pain, vomiting, diarrhea, abdominal pain, or unexplained hemorrhage; and (2) an epidemiologic risk factor within the 21 days before the onset of symptoms” (CDC, 2015, “Epidemiologic Risk”). Epidemiologic risk factors include: Direct exposure to blood or body fluids from a person with Ebola; providing direct care to a living or deceased Ebola patient in a household or medical setting without appropriate PPE; being in close contact or being in a patient care area of an Ebola patient while not wearing appropriate PPE; or traveling to countries with widespread transmission of EVD (CDC, 2015, “Epidemiologic Risk”).

Typical Course of Illness

EVD, which was originally referred to as Ebola Hemorrhagic Fever, is a severe and acute viral infection characterized by a sudden onset of fever, shock, and coagulation defects (Public Health Agency of Canada, 2015). Recent studies have shown that the typical course of infection due to EBOV begins at the cellular level, wherein the virus affects the viral replication of macrophages, monocytes and dendritic cells. As a result of the disturbance, the activation of a systemic inflammatory response syndrome and innate immunity causes massive destruction to vital organs, vascular damage, and hemorrhage (Richardson et al., 2010). Although Ebola is known for its lethality, its severity varies from individual to individual; for some it is fatal, some may survive, and some may never develop any symptoms (Ezenwa et al., 2015).

Patients infected with EBOV usually have an abrupt onset of fever and symptoms typically 8-12 days postexposure. The incubation period of EVD varies from 2-12 days with a mean of 8-12 days after exposure. The initial signs and symptoms are nonspecific and generally include fever, chills, malaise, myalgia, and an elevated body temp; because of these nonspecific symptoms in the early stages of the disease, EVD is often mistaken for other more common infections such as typhoid fever, malaria, meningococcemia, and other bacterial infections like pneumonia. Five days after the manifestation of nonspecific symptoms, patients often progress to gastrointestinal symptoms that include: Severe watery diarrhea, nausea and vomiting, and abdominal pain. Patients may also experience chest pain, headaches, confusion, shortness of breath, hiccups, seizures, and edema. Bleeding is not universally present (has only been reported in 18% of patients and often found in the stool) but can present later in EVD progression as petechiae, ecchymosis, or oozing from venipuncture sites and mucosal hemorrhage. By day 5-7, patients may begin to develop diffuse erythematous maculopapular rashes which usually involves the arms, neck, and trunk. Spontaneous miscarriages may also be experienced by pregnant women (CDC, 2015, “Ebola Virus Disease”). Fatality from EVD is usually accompanied by severe clinical signs early during the infection and patients usually die between day 6-16 of complications (with a mean of 7.5 days) most often due to low blood pressure levels from fluid loss (McKenna, 2015). Risk factors that are associated with a fatal outcome includes: Unexplained bleeding, age 45 years or older, confusion, hiccups, coma, and a number of other signs and symptoms. Those who survive EVD usually have fever for several days before improvement, which typically occurs around day six (CDC, 2015, “Ebola Virus Disease”).

Procedures Used to Confirm the Infection

The early diagnosis of EBD is difficult because its early symptoms are nonspecific and are often seen in more common diseases like typhoid fever or malaria. However, public health authorities must be notified and the patient must be isolated if they present with early symptoms of Ebola and have had contact with: Infected primates or fruit bats; objects that have been contaminated with body fluids of a current or deceased Ebola patient; blood or body fluids of an infected person; or semen from a man who has recovered from EVD. Once a patient has been isolated and authorities have been notified, samples from the patient may be obtained and tested to confirm EDV. EBOV can only be detected in the blood after the onset of symptoms, specifically fever, because of the increase in circulating viruses within the victim’s body. It may take up to three days for the EBOV to reach detectable levels. Antigen-capture ELISA testing, IgM ELISA, polymerase chain reaction (PCR), and virus isolation diagnosis tests are used to detect the infection within a few days after symptoms begins. If the patient is in the later stages of the disease course or have recovered, IgM and IgG antibodies testing is used. If the patient has died, immunohistochemistry testing, PCR, or virus isolation can be used to confirm the infection retrospectively (CDC, 2015, “Diagnosis”).

Vaccine

According to the Centers for Disease Control and Prevention, there is currently no FDA-approved vaccine or antiviral drugs that is available for the Ebola Virus Disease and the development of a preventive vaccine has not been a priority until recently due to the 2014 outbreak.; the virus is now considered a category A biological threat. Although no vaccines have been developed, recent studies have shown promise for, “a combination of monoclonal antibodies and for a small interfering RNA compound (BCX4430) as postexposure prophylaxis in nonhuman primates” (Rio et al., 2014).

Due to the recent infection of EBOV by foreign nationals, there has been a lot of attention brought to Zmapp, a combination of monoclonal antibodies, which is also an unlicensed drug in the early stages of testing. Zmapp is produced on tobacco leaves, however, the process has been slow and product shortage has become a problem. Blood plasma from EVD survivors is also thought to be a useful way of providing immunity, but it has been reported to be unsuccessful and is also in short supply and can possess risks such as Hepatitis B and HIV. The focus now is to accelerate the trials of potential vaccines against the Zaire strain. Although it is only in the early stages of development, it has been shown to produce positive results in non-human primates (Boulton, 2015).

Treatment Options

Currently, there is no cure for the Ebola Virus Disease; those who have contracted Ebola can only be provided with supportive care. Unfortunately, it is almost near impossible to deliver adequate care of EVD victims in West Africa as of current. There is limited access to basic healthcare equipment and tertiary care facilities are sparse. The symptoms of EVD and its complications are treated as they present themselves. Basic interventions, if used early, can maximize the chances of survival in an EVD patient (CDC, 2015, “Treatment”). Maximum Use of Supportive Therapies (MUST) involves intravenous fluids, nasogastric tube feeding, electrolyte replacement, and access to drugs to limit vomiting and to manage secondary sepsis. Emphasis has been placed on providing improved supportive care and less on experimental therapies (Casey, 2015). Alternative therapy practitioners on the internet have made claims about EDV and its cure. Of these claims, some popular ones include mega doses of vitamin C and essential oils, as well as the promotion of homeopathy, and herbalism. However, despite these claims, there have been no clinical trials in the management of Ebola Virus Disease. (Casey, 2015).

Fictitious Scenario of Cluster

G.S., a man living in Sierra Leone, hunts for bush meat. Unbeknownst to him, the animal he has caught is a fruit bat that had been infected with the Ebola virus. He brings it home and cooks it for his wife, son, and grandma to eat. As he cooks the meat over a fire that he had built, a rare downpour of rain sweeps over his hometown and puts out all the fires of the village. He has no energy after a long day of hunting to restart the fire so he deems the meat cooked well enough to eat, although some parts are still raw. His family eats and goes to bed. A few days later, his entire family as well as himself falls ill and they are taken to a local hospital in the village to be treated. The unsanitary conditions of the hospital prove the be the perfect Petri dish for the virus as the doctor examines the family and fails to properly wash his hands and sanitize his equipment as he moves on to work with his next patient. After a full 12 hours of operation, the doctor has effectively infected all of his patients with the virus due to lack of proper sanitation and use of precautionary measures; he has spread bodily fluids from one patient to another. He has also contracted the virus through an open cut on his finger that he had failed to cover up before treating G.S and his family. G.S. goes home untreated and his cousin, who lives in a neighboring village, comes over to provide care for the family in hopes that they would recover. As his cousin cares for the family, he himself contracts the infection as well in which he takes back to his village where he infects his family and friends. Over the course of a couple of weeks, G.S. and his family pass away and others who had been treated by the doctor fall ill. Those who attended the family funeral also become affected as they weep over the bodies, kissing and hugging them. Those who have been infected all go to the hospital where the healthcare workers lack proper protective equipment and knowledge of the disease. The nurses and doctors all contract the illness in which they pass onto other unsuspecting patients. Over the course of just a few weeks, hundreds, and maybe even thousands of people in West Africa are infected, starting the world’s largest Ebola outbreak.

Prevention Plan (Primary, Secondary, Tertiary)

Primary prevention is imperative in the fight against the spread of a disease. When taking into consideration regions such as West Africa where Ebola is prevalent, there must be considerable attention put forth to proper education, disease information dissemination, and healthcare access. Effective and culturally competent education on the spread of EVD, it’s symptoms, and how avoid contracting it can drastically prevent the spread. The general public and healthcare providers that may deal with an Ebola case must know how to recognize signs and symptoms of an infection and how to properly handle the situation and take necessary precautions in order to prevent its transmission. Another primary prevention method would be to impose travel restrictions and checks on all travelers coming in from areas where Ebola is present. Many countries have already barred outside visitors from areas that have reported cases of Ebola. Another way would also be to educate travelers on possible risks of traveling abroad and the proper precautions that need to be taken.

Secondary prevention in regards to Ebola focuses on detection and intervention with those who have already contracted the virus. Secondary prevention is imperative in the fact that it includes early detection and screening which allows for proper measures to be taken to prevent the virus from spreading from someone who already has it to someone who is healthy. This will include early screenings like stool sampling or blood work, as well as early recognition of PUIs. Those who are suspected of having Ebola (PUIs) must be screened, diagnosed, and quarantined to prevent further spread. Early detection and screening also allows health care works as well as care givers and family members knowledge of the presence of infection in order to prepare and take proper precautions when dealing with the patient. This may include the use of PPE or quarantining the patient. Secondary prevention may also include early detection and screening needed to provide proper medical attention to the patient before EBOV advances in the body, possibly becoming fatal.

Tertiary prevention is imperative to provide quality care in those who have already contracted Ebola, to manage their condition and enhance their quality of life. Although there is no cure for Ebola as of current, supportive care must be implemented. This includes “managing hypovolemia, correcting electrolyte imbalance, maintain blood pressure and oxygenation, pain relief, treating secondary bacterial infections, support/replacement of organ functioning, and managing DIC and cerebral edema” (Casey, 2015). It is also important to monitor the patient and their condition in order to learn from the disease and make future adjustments as to how healthcare providers can better care for patients. Patients may also be enrolled in studies to find cures and vaccine to prevent future outbreak.

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