EBOLA: The VirusDr Sandeep DograMD, MNAMS

Assistant ProfessorDept. of MicrobiologyGovt. Medical College, Jammu

Outbreak anywhere can be a risk everywhere- Thomas R Frieden, CDC, Atlanta, USA

Overview

•The agent•Taxonomy•Reservoir•Transmission•Pathogenesis

The agent• Enveloped, non-segmented,

negative-stranded RNA virus• Prototype Viral Hemorrhagic

Fever Pathogen• First appeared in 1976 in 2

outbreaks • Derived it’s name from a river

in Congo called Ebola• Caused more than 20

outbreaks in Africa since than

Taxonomy• Order: Mononegavirales• Family: Filoviridae• Genus: Ebola like viruses• Species: Ebola• Subtypes:

▫ Zaire Ebola virus - Democratic Republic of Congo (1976)▫ Sudan Ebola virus - Sudan (1976) ▫ Reston Ebola virus - Philippines (1989)▫ Tai Forest Ebola virus - Ivory Coast (1994) ▫ Bundibugyo Ebola virus - Uganda (2007)

C.M. Fauquet (2005). Virus taxonomy classification and nomenclature of viruses; 8th report of the International Committee on Taxonomy of Viruses

Reservoir of infection

• Zoonotic virus• Fruit bats - most likely

reservoir▫ Hypsignathus monstrosus▫ Epomops franqueti▫ Myonycteris torquata

• Others - Chimpanzees, gorillas, monkeys, forest antelope and porcupines

• Limited evidence that wild dogs/cats become infected

Transmission• In Africa, Ebola may spread as a result of

hunting, processing, and consuming infected animals (e.g., bush meat)

•Human-to-human transmission of Ebola virus via inhalation (aerosols) has NOT been demonstrated

•Remains from deceased infected persons are highly infectious

•Close contact and health care workers get frequently infected while treating the patient

Human to human transmission• Virus present in high quantity in blood, body

fluids, and excreta of symptomatic patients• Opportunities for human-to-human

transmission▫Direct contact (through broken skin or

unprotected mucous membranes) with an EVD-infected patient’s blood or body fluids

▫Direct contact with the corpse of a person who died of EVD

▫Sharps injury (with EVD-contaminated needle or other sharp)

▫Indirect contact with an EVD-infected patient’s blood or body fluids via a contaminated object (soiled linens or used utensils)

Pathogenesis

•Incubation period ranges between 2-21 days

•Onset of symptoms to death: 6-16 days•Mortality rates: 25-90% depends on Ebola

strain•Zaire strain most virulent - mortality up to

90%•People are infectious as long as their

blood and secretions contain the virus WHO. Ebola virus disease. Fact Sheet No. 103. Geneva: World Health Organisation, 2014.

Pathogenesis

•Molecular basis of virulence not known•Direct infection of tissues•Immune dysregulation•Hypovolemia and vascular collapse

▫Electrolyte abnormalities▫Multi-organ failure, septic shock

•Disseminated intravascular coagulation (DIC) and coagulopathy

Lancet. Mar 5, 2011; 377(9768): 849–862.

Direct infection of tissues

•Infects many cell, including monocytes, macrophages, dendritic cells, endothelial cells, fibroblasts, hepatocytes, adrenal cortical cells and epithelial cells.

•Virus migrates from the initial infection site to regional lymph nodes and subsequently to the liver, spleen and adrenal gland.

Immune dysregulation

•High mortality rate believed to be the result of virus proteins capability of defeating the immune system by:▫Complement mediated antibody-dependent

enhancement of infection▫Inhibition of multiple interferon pathways▫Infected macrophages inducing apoptosis

in lymphocytes

Hypovolemia and DIC•Adrenocortical necrosis also occurs and is

associated with hypotension and impaired steroid synthesis

•Hepatocellular necrosis leads to dysregulation of clotting factors and subsequent coagulopathy

•Virus appears to trigger a release of pro-inflammatory cytokines with subsequent vascular leak and impairment of clotting ultimately resulting in multi-organ failure and shock .

Philippe CalainChief Epidemiologist CDC Special Pathogens Branch

"At the end of the disease the patient does not look, from the outside, as horrible as you can read in some books. They are not melting. They are not full of blood. They're in shock, muscular shock. They are not unconscious, but you would say 'obtunded', dull, quiet, very tired. Very few were hemorrhaging. Hemorrhage is not the main symptom. Less than half of the patients had some kind of hemorrhage. But the ones that had bled, died" 

Summary•Humans are actually just an accidental host•Human-to-human transmission by direct

contact▫No human-to-human transmission via

inhalation (aerosols) ▫No transmission before symptom onset

•Greater risk for India because of the number of Indians working in West African nations

•Constantly changing genetic makeup of the Ebola virus means it will spread at a much greater speed. 

More information…

www.cdc.gov www.who.int

Thank you Ebola For making us realize that how much we interfere with nature

and how much we are prepared for any eventuality.