Ebola Without Borders

The following facts regarding Ebola were obtained from the website UptoDate.com.

The material was pruned from the source in order to make it more readable to lay readers. With so much misinformation banded about, it is my hope that these facts will stem the tide of irrational fear.

 

The Ebola virus belongs to the Filovirus family of viruses.

As such they are among the most virulent pathogens known.

The term Filovirus is derived from the Latin word "filum", a word to indicate 'thread-like'. It was chosen because of the filamentous structure of the virus.

Ebola viruses cause severe disease and have a fatality rate of over 70 percent.

Ebola virus is named after the Ebola River that runs through Zaire and where the first virus was found.

There is no therapy available for the treatment of Ebola diseases, but progress has been made in developing a vaccine.

It was once a mystery as to the identity of the original host and the mode of transmission from that host to humans.

It now appears that Ebola viruses were first hosted by bats.

Bats are present in large numbers at the sites of several filovirus outbreaks and are known to host other pathogenic RNA viruses, such as rabies.

Fruit bats are the likely original host of the virus and the partially digested fruit that is dropped by the bats and eaten by animals is the most likely method by which iti s transmitted to humans and other primates.

Classification of Ebola Viruses


Ebola viruses are single-stranded RNA viruses that require the enzyme reverse transcriptase in order to replicate.

Ebola virus causes hemorrhagic fever whose clinical manifestation include coagulation defects, capillary leaks and septic shock.


Ebola viruses are divided into five different species; the Zaire, Sudan, Ivory Coast, Bundibugyo, and Reston agents.

They each differ in their virulence to humans.

The Zaire species has caused large outbreaks of disease with mortality rates of up to 90 percent. It was first identified in 1976

The Sudan virus has a 50 percent fatality rate based on the four known epidemics it has been involved in.

The Ivory Coast virus has only been the causative agent in one case and that person survived.

The Bundibugyo virus caused an outbreak of hemorrhagic fever in Uganda in 2007 and has a fatality rate of under 30 percent. Sequencing the genome of this virus has shown that it is closely related to the Ivory Coast virus.

The fifth Ebola species, the Reston virus, differs markedly from the others, because it has not been found in Africa but rather in the Philippines.

Ebola Reston virus caused an outbreak of lethal infection in macaques, a type of Old World monkey. 

The outbreak occurred when they were imported into the United States in 1989 and brought worldwide attention to the filovirus family with the publication of Richard Preston's book, The Hot Zone.


Outbreak of Ebola Virus Disease

Filovirus first appeared in 1967 with the inadvertent importation of infected monkeys from Uganda into Germany and the former Yugoslavia. This resulted in explosive outbreaks of illness among vaccine plant workers who prepared primary cell cultures for polio vaccine production.

The workers came into direct contact with the animals by killing them and removing their kidneys.

Since then, all outbreaks of Ebola disease have occurred in sub-Saharan Africa with increasing frequency since 1990.


The 2014 Outbreak

By far, the largest outbreak of Ebola virus disease is currently occurring in West Africa with the Zaire species, the active agent.

Although most previous Ebola outbreaks occurred in Central Africa, this outbreak started in the West African nation of Guinea in Decemeber 2013 and was confirmed by the World Health Organization (WHO) in March 2014.

The index patient was a two-year-old child in Guinea, who developed fever, vomiting, and black stools. Four days later, the child was dead.

The outbreak subsequently spread to Liberia, Sierra Leone, Nigeria, Senegal, and Mali.

Analysis of the viruses indicated that the disease resulted from person-to-person contact and has a mortality rate of 70 percent.


The  extent of the outbreak has been underestimated due to the flood of victims of Ebola virus disease being cared for outside of hospitals, where their deaths go unreported.

As the last days of October 2014 pass, the number of probable and suspected cases attributed to Ebola virus is close to 10,000, half of which have died.

This includes almost 500 healthcare workers, of whom half have died.

On a positive note, Nigeria and Senegal have not reported any new cases since September and have been declared Ebola-free by the World Health Organization.


On September 30, 2014, Thomas Eric Duncan became the first Ebola victim in the United States.

He had traveled from Liberia to Dallas, Texas where he developed Ebola virus symptoms five days after his arrival.

The patient was asymptomatic prior to and during the flight.

Two nurses, Nina Pham and Amber Vinson, who were involved in his care subsequently developed Ebola virus disease. They were successfully treated and declared Ebola-free as October 2014 came to a close.

At about the same time, Dr. Craig Spencer returned home to New York City after a stint in Guinea with the organization, Doctors Without Borders where he treated Ebola disease patients.

The doctor set off a firestorm of controversy and a torrent of panic by his reckless behavior in violating the first rule for physicians, do no harm.

His blatant disregard for established protocols of remaining quarantined in the comfort of his home allowed politicians to do what they do best.

Involve themselves in things they have no knowledge of.


Transmission of Ebola Disease

Filoviruses are thought to initiate infection via ingestion, inhalation, or passage through mucosa and breaks in the skin.

Human infection can also result from the inadvertent transfer of virus by the patient's own contaminated hands.


Person-to-person transmission of the Ebola virus occurs through contact with virus-containing body fluids of a person who has signs and symptoms of illness.

The virus is transmitted via broken skin or unprotected mucous membranes.

The most infectious body fluids that contain the virus are the blood, feces, and vomit of an Ebola patient.

Ebola virus has also been detected in urine, semen, and breast milk while saliva, sweat and tears may also harbor the virus/

Contact with any of these fluids poses a potential risk.


Transmission in Africa is often due to the ritual of washing Ebola victims at funerals and touching them as they prepare the body for burial.

Healthcare workers are at risk of infection if they care for a patient with Ebola virus disease without appropriate protective measures.


Ebola virus may also be transmitted though contact with previously contaminated surfaces and objects.

Ebola virus is thought to exist for up to several days on surfaces but its potential risk can be reduced by proper cleaning.


Ebola virus disease is rarely, if ever, spread from person to person through the respiratory route.

Although aerosolized filoviruses are highly infectious for laboratory animals, in humans, airborne transmission has only been reported among healthcare workers who were exposed to aerosols generated during medical procedures.

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Prior to the epidemic in West Africa, outbreaks of Ebola virus disease were typically contained within a period of weeks to a few months.

This was generally attributed to the relatively inefficient person-to-person transmission of the virus in areas of the African rainforest where population density was low and residents rarely traveled far from home.

This epidemic however, has shown that Ebola virus disease can spread rapidly and widely due to the extensive movement of infected individuals. This is especially true for the undetected who travel across national borders and those who avoid isolation and quarantine.

Infection with Ebola virus occurs through contact with animals via the hunting, butchering, or preparing meat from infected ones. To prevent this type of infection, food should be properly cooked since the Ebola virus is inactivated through cooking.

Transmission of Ebola virus to healthcare workers occurs when appropriate personal protective equipment is not available or not properly used. In fact, during the outbreak in West Africa, a large number of healthcare workers developed Ebola virus disease, due  to a lack of personal protective equipment and exposure to patients who had Ebola virus disease.

'These are known as nosocomial transmissions and indicates that it is the patients who transmitted the Ebola virus to the healthcare workers who cared for them.

It shoulod be pointed out that Ebola viruses are not carried by mosquitoes or other biting insects.

Pathogenesis of Ebola Disease

 

Ebola virus enters the body through mucous membranes or breaks in the skin.

The virus infects almost every cell type in the body. The list includes monocytes, macrophages, dendritic cells, endothelial cells, fibroblasts, hepatocytes, adrenal cortical cells, and epithelial cells.


Whatever port of entry the virus uses to enter the body, macrophages are probably the first cells to be infected.

The virus replicates within these "sentinel" cells and causes death to the cells and the release of a large numbers of new viral particles.  The virus then spreads to regional lymph nodes and undergoes another round of replication. This is followed by virus infection of dendritic cells and macrophages located in the liver, spleen, thymus, and other lymphoid tissues.


Rapid spread is aided by virus-induced suppression of type I interferon response. As the disease progresses, hepatocytes, adrenal cortical cells, fibroblasts, and many other cell types become infected. This results in extensive tissue damage

 In addition to causing extensive tissue damage, filoviruses also induce a systemic inflammatory syndrome by inducing the release of cytokines, chemokines, and other pro-inflammatory mediators from the infected macrophages.

Macrophages infected with Ebola Zaire virus produce tumor necrosis factor,  interleukin, and macrophage chemotactic protein. It is thus the host response to infection, rather than the toxic effect of the virus, that is responsible for the fever, malaise, vasodilatation, increased vascular permeability, hypotension, and shock associated with Ebola disease.

Virus-infected macrophages synthesize cell-surface tissue factor  which triggers the coagulation defects that occur in Ebola disease. In addition, the pro-inflammatory cytokines also induce macrophages to produce the same tissue factor. This simultaneous occurrence explains the early appearance and rapid development of the coagulopathy of Ebola virus infection.


Clinical Manifestations of Ebola Disease

 Over the 40 years since Ebola virus was first discovered, a number of clinical features of Ebola virus disease have been documented. One in particular seemed odd. Despite its name, Ebola hemorrhagic fever, bleeding is not common and is typically only seen in the terminal phase of the disease.

In the present West Africa epidemic, the term Ebola virus disease is used instead of Ebola hemorrhagic fever.

Patients with Ebola virus disease typically have an abrupt onset of symptoms anywhere from 8 to 12 days after exposure although the range of 2-21 is often sited.

There is no evidence that asymptomatic persons, while the virus is still in the incubation period, are infectious.

Symptomatic individuals are  assumed to have high levels of virus in their blood and other body fluids and so all safety precautions need be taken.

Signs and Symptoms of Ebola Virus Disease

Ebola disease patients begin with influenza-like symptoms, which then rapidly progresses to full-blown organ failure and septic shock.

The most common symptoms reported from West Africa during the 2014 outbreak are fever, fatigue, vomiting and diarrhea.


There is usually an abrupt onset of fever, chills, and malaise. Other signs include weakness, anorexia, and severe headaches. Some even develop a rash by the fifth day f of illness. The rash usually involves the face, neck, and arms.


Watery diarrhea, nausea, vomiting, and abdominal pain are frequently found within a few days of infection. This despite the warning that the infection can take up to 21 days. 

Bleeding does not often occur in the early phase of illness but manifests itself later in the disease with frank hemorrhaging seen only in the terminal phase of ithe disease.


In non-fatal cases, patients improve approximately 6 days after the onset of symptoms.

Death typically occurs between a week or two after symptoms first appear.