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Ebola Virus


OVERVIEW OF Ebola Virus :

Ebola virus disease (EVD) is a deadly disease with occasional outbreaks that occur mostly on the African continent. The virus is most common among the people and non human primates( such as monkeys, gorillas and chimpanzees).


STRUCTURE of Ebola Virus :

 

  • Structure of Virus:

Flaviviridae

 

                        Morphology

      • Viruses of Flaviviridae family are Spherical viruses.
      • Size: 40 – 50 nm in diameter.
      • Genetic Material :- (+) ssRNA.

            Classification

    • Some members of Flaviviridae are Mosquito-borne while others are Tick-borne
    • Hepatitis C virus is neither mosquito nor tick-borne.
    • Mosquito-borne Flaviviruses
      1. Encephalitis viruses
        1. St. Louis Encephalitis Virus
        2. Ilheus Virus
        3. West Nile Virus
        4. Murray Valley Encephalitis Virus
        5. Japanese B Encephalitis Virus
      2. Yellow Fever
      3. Dengue
    • Tick-borne Flaviviruses
      1. Tick-borne Encephalitis viruses
        1. Russian Spring-Summer Encephalitis
        2. Powassan Virus
      2. Tick-borne Hemorrhagic Fevers
        1. Kyasanur Forest disease (KFD)
        2. Omsk Hemorrhagic fever


CAUSES :

It is caused by the virus belonging to the Flaviviridae and ebolaviridae family.

In Africa people tends to develops ebola virus after handling infected animals which is found ill or dead, including chimpanzees, gorillas, fruit bats, monkeys, forest antelopes and porcupines.

The human to human transmission occurs after someone infected with the ebolavirus. The incubation period of the virus ranges from 2 and 21 . After 21 days it takes the symptoms to develope.  The outbreaks may spread rapidly.


PATHOPHYSIOLOGY :

Arbovirus enter cells by receptor-mediated endocytosis and exit by budding from

the plasma membrane.

Arbo viruses enter the body via mosquito bites and replicate in various tissues,

including Langerhans cells, which then migrate to lymph nodes, causing viremia.

Viremia results in invasion of the central nervous system (CNS) by arbovirus that

cause encephalitis and meningitis or of the joints and internal organs by viruses that cause fever,

arthralgia, and rash.

All arbovirus suppress the innate immune response by inhibiting JAK/STAT

signaling, a major early determinant of disease severity.

At later times, recovery is mediated by virus-neutralizing antibodies and cytotoxic T cells.

The viruses are capable of boosting the immune system of the host cell and aids in the production of interferons.

Ebola virus enters the patient through mucous membranes, breaks in the skin, or parenterally and following cells are gets infected.

 The cells might include monocytes, macrophages, dendritic cells, endothelial cells, fibroblasts, hepatocytes, adrenal cortical cells, and epithelial cells.

 The incubation period may be related to the infection route (6 days for injection versus 10 days for contact).

 Ebola virus moves from the initial infection site to regional lymph nodes and might subsequently passes to the liver, spleen, and adrenal gland.

 Although not infected by Ebola virus, lymphocytes undergo apoptosis resulting in decreased lymphocyte counts.

Hepatocellular necrosis occurs and is associated with dysregulation of clotting factors and subsequent coagulopathy.

 Adrenocortical necrosis also can be found and is associated with hypotension and impaired steroid synthesis.

 Ebola virus appears to trigger a release of pro-inflammatory cytokines with subsequent vascular leak and impairment of clotting ultimately resulting in multiorgan failure and shock


ROUTES OF TRANSMISSION :

Transmission of Ebola between humans can occur through:

  • Direct contact through breach in the skin and mucous membranes with the blood, secretions, organs, or other body fluids of infected people.
  • Indirect contact with the environments which is contaminated with such fluids.
  • Exposure to the objects which are at higher risk, such as needles.
  • Burial ceremonies in which mourners have direct contact with the body of the deceased.
  • Exposure to the semen of people with Ebola or who have recovered from the disease – the virus can still be transmitted through semen for up to 7 weeks after recovery from illness.
  • Contact with patients with suspected or confirmed EVD – healthcare workers have frequently been infected while treating patients.


COMMON CLINICAL SIGNS AND SYMPTOMS :

The time interval from infection with Ebola to the onset of symptoms is 2-21 days, although 8-10 days is most common. Signs and symptoms include:

  • fever
  • headache
  • joint and muscle aches
  • weakness
  • Diaarhoea
  • vomiting
  • stomach pain
  • lack of appetite

Some patients may experience:

  • rash
  • red eyes
  • Hiccups
  • cough
  • sore throat
  • chest pain
  • difficulty breathing
  • difficulty swallowing
  • bleeding inside and outside of the body


DIAGNOSTIC :

Detection of virus-neutralizing antibodies in combination with recent travel history to an

endemic area may be meaningful.

Immunosorbent assay- detect the virus specific IgM or IgG antibodies.

Greater than fourfold rise in titer between acute and convalescent sera  and  cerebo spinal fluid containing virus specific IgG or IgM or both are the diagnostic features. It is used to detect the virus specific IgM or IgG antibodies.

Greater than fourfold rise in titer between acute and convalescent sera and cerebo spinal

fluid containing virus specific IgG or IgM or both are the diagnostic features.

Real-time polymerase chain reaction (RT-PCR)- is valuable in the early confirmation of arbovirus infections, particularly chikungunya. However, the value of RT-PCR is limited to diagnosis in the viraemic phase, with later infection requiring serology. It is very much useful in early detection of the virus. The value of RT-PCR is limited to diagnosis in the viraemic phase, with later infection requiring serology.

A normal erythrocyte sedimentation rate- and a negative rheumatoid factor are useful to differentiate chikungunya arthritis from rheumatoid arthritis. Extensive, symmetrical joint involvement, particularly of the metacarpophalangeal and proximal joints, the presence of rheumatoid nodules or anti-cyclic citrullinated peptide (anti-CCP) antibodies favours rheumatoid arthritis over chikungunya with chronic arthropathy. The presence of lower limb asymmetrical joint involvement with axial skeletal affliction favours the diagnosis of spondyloarthropathy over chikungunya.

Complement fixation test:

A complement fixation test is the test which provides antigen to antibody reactions.

Blood test: 

To check for  any abnormalities in the brain proteins.

Biopsy:

 Through a small hole in the skull, a doctor uses a needle to take a sample of tissue from the infected site.

Imaging tests: 

CT scan, MRI scan SPECTs and  PET scans help doctors locate the any damage to the brain .

Neurological exam: 

The doctor might look for any abnormalities such as changes in the movements, speech and other co ordination of the movements.

Spinal tap:

A doctor uses a small needle to remove fluid from around the spine. A laboratory examines this fluid to look for cancer cells.


TREATMENT AND PROGNOSIS :

Treatment:

The main aim is to restore the body fluids and electrolytes

If needed blood transfusions or fresh frozen plasma can be transferred

Inmazeb is a mixture of three monoclonal antibodies (atoltivimab, maftivimab, and odesivimabebgn).

 Ansuvimab is a monoclonal antibody given as an injection. It helps block the virus from the cell receptor, preventing its entry into the cell.

Vaccines:

The vaccines are developed by the FDA are only the strains for Zaire ebolavirus.


PREVENTION :

Animals should be contacted carefully and the food, meat should be cooked or should be heated properly to prevent from infection or contamination

Use proper gloves and personal protective equipment to prevent from human to human transmission.

Safe method of disposing the dead bodies of the infected persons.

To follow safe sexual practices.

Frequent antenatal care visits is essential in patients who are pregnant.