Monday, January 19, 2015

EBOLA VIRUSE DISEASE


WHAT   IS   EBOLA   VIRUSE   DISEASE?

Ebola virus disease is also called Ebola hemorrhagic fever with case fatality rate upto 90%; it is a disease of humans and other primates caused by Ebola viruses.

ALTERNATIVE NAMES:

Ebola Hemorrhagic fever, Ebola virus infection, Viral Hemorrhagic fever, Ebola.

HISTORY:


First outbreak of EVD was reported in 1976 in Nzara, Sudan, infected 284 of people and killed 151. After the outbreak in Nzara and Yambuku, it occurred in village near Ebola River, from which disease takes its name. Now a days it takes an importance due to its largest outbreak in West Africa, infected 17,590 of people and killed 6,556.

SIGNS AND SYMPTOMS:


After the exposure to the virus the incubation period ranges from 2 to 21 days.
 
• Early symptoms are non specific, begins with sudden influenza, tiredness, fever (38.3ᵒ), weakness, decreased appetite, muscle pain, joint pain, headache, sore throat.


• After 5 days it is followed by vomiting, diarrhea, abdominal pain.


• Next, shortness of breath, chest pain may also occur, along with swelling, headaches and confusions. Flat  red areas covered with small bumps are also developed on skin in half of the cases. 


•Internal and external bleeding may occur due to decreased blood clotting ability. External bleeding is characterized by vomiting of blood, coughing up of blood, blood in stool. Internal bleeding is characterized by bleeding into whites of eyes and bleeding into skin (hematomas).


• Death occurs due to low blood pressure from fluid loss.


• Those who survive have ongoing muscle and joint pain, liver inflammation, decreased hearing. They also develop antibodies against Ebola that last at least 10 years. If someone survives Ebola, they can no longer transmit the disease.





STRUCTURE OF EBOLA:


 EBOV carries negative sense RNA genome in virions that are cylindrical/tabular, and contain viral envelope, matrix and nucleocapsid components.
 
• The cylinders of virions are 80nm in diameter, 800nm in length and have viral encoding glycoprotein projecting as 7-10 nm long spikes from its lipid bilayer surface. 


•The outer viral envelop is derived by budding from domains of host cell membrane into which the GP spikes have been inserted during their biosynthesis.


• Viral proteins VP40 and VP24 present in matrix space between the envelop and nucleocapsid.


• Nucleocapsid is present at the centre which is composed of series of viral proteins attached to negative sense RNA.

LIFECYCLE OF EBOLA:


Virus first attacks and invades dendrites, cells that alert the body to infection. Due to this activity virus can deceive the immune system and starts to replicate itself. Then infected cells start to rupture and releasing more virus particles into body along with the release of inundate of cytokines. Cytokines cause fever, inflammation and internal bleeding due to damage to blood vessels. Certain white blood cells called neutrophils, which basically fight against an infection, in this case it act as carrier of Ebola virus and spread Ebola throughout the body. After the virus has spread throughout the body, death is attributed to severe blood loss and organ failure.

TRANSMISSION:


Fruit bats of Pteropodidae family are considered as natural host of Ebola virus. It is introduced into the human population through close contact with secretions, blood, organs, or other bodily fluid of infected animals such as chimpanzee, gorillas, fruit bats, and monkeys.
 Then it spreads through human to human transmissions via direct contact with blood or body fluids such as saliva, sweat, mucous, vomit, feces, tears, breast milk, urine and semen, of a person who has developed the symptoms of disease. An entry point for virus includes nose, mouth, eyes, open wounds, and abrasions. Ebola may be spread through large droplets, in case when person is extremely sick. Contact with surfaces and objects contaminated by virus like needles, syringes may also transmit the infection. Burial ceremonies also play an important role in the transmission of Ebola. It may be transmitted while treating the patient without practicing any precautionary measures.

Transmission of Ebola through airborne route, water, food other than bush meat has not been reported. No spread by mosquito and other insects has been reported. The lack of airborne transmission is believed to be due to low level of virus in lungs and other parts of respiratory organs of primates, insufficient to cause new infections. In the case of pigs, the transmission of Ebola virus through airborne route has been reported just because of high concentration of Ebola virus in their lungs, not in their blood stream.




DIAGNOSIS:


It can be difficult to distinguish EVD from other infectious diseases like malaria, typhoid fever, meningitis. Confirmations that symptoms are caused by Ebola virus are made by using these investigators.
 
• Antibody-capture enzyme-linked-immunosorbent assay (ELISA)


• Antigen capture detection tests


• Serum neutralization test


• Reverse transcriptase polymerase chain reaction (RT-PCR) assay


• Electron microscopy


• Virus isolation by cell culture


First of all travelling, work history and exposure to wildlife of a suspected person must be taken into consideration before any medical examination.

Initial laboratory testing includes platelets count, white blood cells count, checking the level of liver enzymes. In case of EVD a patient experiences low platelets count, initially decreased white blood cells count, followed by increased white blood cells count, elevated levels of liver enzymes (alanine aminotransferase, aspartate amino transferase ) and abnormalities in blood clotting often consistent with dissiminated intravascular coagulation, such as prolonged prothombin time, partial thrmboplastin time and bleeding time.

Then isolating the virus by cell culture, detecting its RNA by PCR, its proteins by ELISA, and also its antibodies for the detection of Ebola virus. In case of antibodies detection, IgM antibodies can be detected two days after symptom onset and IgG antibodies can be detected 6 to 18 days after symptom onset. Ebola virus can also be detected by using electron microscope due to its filamentous shapes in cell culture.

PREVENTION:


 Although Ebola virus is a dangerous virus but can be easily avoided by following ways.
 
• Wear protective clothing like face masks, gowns, goggles, gloves, close toed shoes while handling the patient.


• Wash hands regularly with soap and clean water.


• Infected person should be in barrier-isolation from other people.


• In case of exposure wash with large amount of water, eyewash or chlorine water.


• Avoid physical contact with person showing symptoms and signs.


• Keep away from bats, monkeys, baboons, and dead animals.


• Avoid eating bush meat and animals products should be thoroughly cooked before consumption.


• Only travel to areas where there is an Ebola outbreak in case of urgent need.


• Inform health authorities immediately in case of contact with Ebola case.


• Disinfect clothing and bedding of suspected Ebola patient with bleach.


• Avoid funeral or burial rituals that require handling of someone who has died from Ebola.


• If someone has died from suspected Ebola, don’t wash their bodies, limit unnecessary handling.



TRAETMENT:


There is yet no proven treatment available for EVD. However survival is improved by supportive care with rehydration and symptomatic treatment. These measures include management and treatment of pain, nausea, fever, anxiety and other infections, blood pressure management, and rehydration via oral or intravenous route. The WHO has approved the use of whole blood products such as platelets, packed red blood cells, fresh frozen plasma to treat the people.  The WHO recommends avoiding the aspirin and ibuprofen for pain due to bleeding risk. Interferon therapies and Ribavirin are known to be ineffective against EVD.
No licensed vaccines are available yet for the treatment of EVD.

NEW RESEARCH:


The UNC scientist partnered with researchers from the University of Washington in Seattle and National Institute of Health’s Rocky Mountain Laboratories in Hamilton, MT, to produce new line of mice or new mouse model to accelerate research on potential vaccine and treatment for Ebola. The team worked with eight mouse variants and then they found that some strains do not develop Ebola due to the presence of a gene responsible for encoding the protein TEK and antibodies. Now they are trying to develop antibody therapy for SUDAN strain of Ebola virus by grafting Ebola specific segment of mouse antibody onto human antibody. Still more research is needed.