INTRODUCTION:

A notoriously deadly virus that causes foursome symptoms, the most prominent being high fever and massive internal bleeding ebola virus kills as many as 90%of the people it infects. It is one of the virus that is capable of causing hemorrhagic(bloody) fever(1,2).

Epidemiology:

From 1976-2013, WHO reported 1716 confirmed cases. The largest outbreak in 2014. Wes Africa Ebola virus outbreak which was affected Guinea, Sierra Leone, Liberia, Nigeria, 2127 cases have been identified with 1145 deaths. From 1995-2013 second major outbreak occurred(3).

History:

Ebola virus was first isolated in 1976 during outbreaks of Ebola hemorrhagic fever in Congo and Sudan. The Congo had one of the highest case fatality rates of any human virus 50 to 90%. The name of the disease originates from the Congo which lies on the Ebola river(3,4).

It is primarily considered as a local self- limiting problem with a very high case fatality ratio. Until the end of the eighties there were only remarkable EVD outbreaks (4–7). Changing frequency clearly showed an increase in the risk of development of the EVD outbreak in the next years. Some variability in Case Fatality Ration (CFR) was observed across different outbreaks and a decrease associated with the increase in generations of person to person passage(5,7,8). From December 2013 to August 11, 2015, a total of 20,035 confirmed and probable cases of Ebola virus disease (EVD) were reported in Guinea, Liberia, and Sierra Leone. There have been concerns that the different cultural roles or physiology of male and female persons may have resulted in the sexes being differently affected during this outbreak(9).

Sign and symptoms:

The following 2 types of exposure history are recognized

1. Primary exposure:This is typically involves traveler to or work in an Ebola endemic area.(10–12)

2. Secondary exposure: this refers to human to human exposure(eg. Medical caregivers, family caregivers, person who prepared diseased patient for burial primate to care for primates),or person who collect or prepare bush meat for human consumption.

Physical findings depend on the stage of disease at the time of presentation with African derived ebolavirus infected. There is an incubation period (typically 3-8days) in primary cases and slightly longer in secondary cases.

Symptoms of EVD may appear 2-21days after exposure to the Ebola virus, according to WHO on an average however, symptoms appear within 8-10days.

At first Ebola symptoms seems like those of many other viruses. According to the CDC the patient will usually experience the following symptoms.

A fever greater than 101.5degree Fahrenheit

Muscle pain

Severe headaches

Weakness

Diarrhea

Vomiting

Abdominal pain

Some patients also bleed from the nose and mouth this is called hemorrhagic syndrome and usually occurs only in the late stages of the disease. Typically the ebolavirus causes hemorrhagic syndrome in 30-50%.ofthe patients.

Early finding may include

· Pharyngilis

· Maculopapular rash

· Bilateral conjunctival infection

· Later finding may include

· Expressionless facies

· Bleeding from (IV) puncture sites and mucous membrane

· Myocarditis and pulmonary edema

· In terminally ill patient tachypnea ,HTN, anuria and coma

Diagnosis:

Symptoms that occur in advanced stages of EVD include rash and symptoms of impaired kidney and liver function such as blood in stool according to WHO.

Because of the symptoms of ebola virus are so much like those of other disease. Medical professionals use a series of tests to diagnose EVD(13). According to WHO common tests include the following

a. Virus isolation by cell culture

b. ELISA

c. Serum neutralization test

d. Antigen capture detection test

e. Electron microscopy

f. Reverse transcriptase polymerase chain reaction(RT-PCR) assay

g. Basic blood tests: complete blood count with differential bilirubin, liver enzymes, blood urea nitrogen(BUN), creatinine, PH(16–18)

h. Studies for isolating the virus: tissue culture(only to be performed in one of a few high containment laboratory throughout the world), reverse transcription polymerase chain reaction (RT-PCR) assay

i. Serologic testing: ELISA for antigens or for IgM and IgG antibodies

Viral reservoirs:

Perhaps the greatest mysterious regarding filoviruses are the identity of their natural reservoir and mode of transmission to wild apes and humans. However as the data suggest that bat are least one of the reservoir host of ebolavirus in Africa. (14-16)

Transmission

Epidemics of ebola virus disease are generally thought to begin when an individual becomes infected through contact with meat or body fluids of an infected animal(17–21). Once the patients gets ill or they dies, the virus spreads to others who come into direct contact with the infected individuals blood, skin and other body fluids, the studies in laboratory primates have found that animals can be infected with ebola virus through droplet inoculation of virus into the mouth or eyes suggesting to human infection can result from the inadvertent transfer of virus to these sites from contaminated hands.(22,23)

Person to person:

Person to person transmission associated with direct contact with symptomatic individuals with ebolavirus disease and direct contact with body fluids from patients to EVD.

Risk of transmission through different body fluids:

Transmission is mostly like to occur through direct contact of broken skin or unprotected mucous membranes with virus containing body fluids from a person who has sign and symptoms.

The risk of Ebola transmission also depends upon the quantity of virus in the fluid. During the early phaseof illness the amount of virus in the blood may be quite low but levels then increase rapidly and may exceed 10 to the power 8 RNA copies per ml serum in severely ill patient.(24,25)

· Risk of transmission through contact with contaminated surfaces

· Risk of airborne transmission

· Nosocomial transmission

· Transmission with animals

· Immune response to ebolavirus infection:

Ebola virus replicates at usually high rate that overwhelms the protein synthesis apparatus of infected cells and host immune defenses. Both the adaptive immune and inflammatory system respond to infection at the same time that some cell types specifically monocytes and macrophages are targets relevant to disease pathogenesis. This feature of the infection was initially suggested bythe immune histochemical localization of ebola virus in ivvo endothelial cells mononuclear phagocytes and hepatocytes are the main targets of infection.(26,27)

Vaccine development:

Several animal models have been developed to study the pathogenesis of Ebola virus infection and to assess the efficacy of various vaccine approaches.(28–30)

Genetic immunization with plasmid DNA was developed in the Guinea pig and that was the first vaccine for ebola virus.

In summary, an understanding the mechanisms underlying ebola virus induced cytopathic effects has facilitated the process of vaccine and antiviral therapy development which has in turn provided new information about pathogenesis and the immune response.(31–35)

Prevention:

Prevention focuses on avoiding contact with the viruses. The following precautions can help prevent infection and spread of Ebola and Marburg.

1. Avoid areas of known outbreaks

2. Wash your hands frequently

3. Avoid bush meat

4. Avoid contact with infected people

5. Follow infection control procedures

6. Don’t handle remains.

Treatment and drugs

No antiviral medications have proved effective in treating infection with either virus. Supportive hospital care includes

a. Providing fluids

b. Maintaining B.P

c. Providing oxygen as needed

d. Replacing lost blood

e. Treating other infections that develop(36–38)

CONCLUSION:

Hence, the Ebola virus is studied from various review articles and innovation of the new medication is on the way to medication. Most of the researchers are on the way pre clinically and some of them are succeeded but not clinically approved by FDA and WHO.

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