EbolaThe Deadly African Virus

PAPER-203

Ebola Virus Introduction

• First appeared in Africa 1976

• “African Hemorrhagic Fever” – acute,mostly fatal disease– causes blood vessel “bursting”– systemic (all organs/tissues) – humans and nonhuman primates

• Excluding ‘2000 outbreak– 1,500 cases – over 1,000 deaths

Geography

• The link between human infection by the Ebola virus and their proximity to primates is clear.

-Outbreaks occurred in countries that house 80 percent of the world’s remaining wild gorilla and chimpanzee populations.

- The outbreaks coincided with the outbreaks in wild animals.

- The same distinct viral strains were isolated in animal carcasses and in the bodies of those who handled those carcasses.

- These outbreaks were preceded by an abnormally large death in wild Gorilla populations.

Ebola Taxonomy

Scientific Classification

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

– Ebola-Zaire, Ebola-Sudan,Ebola-Ivory Coast• disease in humans

– Ebola-Reston • disease in nonhuman primates

Copyrighted Dr. Fre:derick A. Murphy, D.V.M., Ph.D. 1976.

Filoviridae or “Filoviruses”

• Most mysterious virus group

• Pathogenesis poorly understood

• Ebola

– natural history/reservoirs unknown

– exist throughout the world

– endemic to Africa

– filamentous ssRNA- (antisense) viruses

Image courtesy of the Centers for Disease Control

MOLECULAR STRUCTURE

• Morphology under electron microscope– filamentous, enveloped RNA virus– approx. 19 kb in length (1 kb = 1000 RNA bases/nucleotides) or 60-80 nm in diameter– single-stranded, linear, non-segmented– negative-sense RNA (encoded in a 3’ to 5’ direction)– appears to have “spikes” due to glycoprotein on outside membrane

• Structure of Ebola genome and proteins– Transcribed into 8 sub-genomic mRNA proteins: 7

structural and 1 nonstructural– 7 structural proteins:

– nucleoprotein (NP)– 4 viral/virion proteins (VP35, VP40, VP30, VP24)– glycoprotein (GP)– RNA-dependent RNA polymerase (L protein)

» NP, VP35, VP30, L protein: required for transcription & replication

» VP40, GP, VP24: associated with the membrane

Ebola Pathogenesis

• Enters Bloodstream– skin, membranes,open wounds

• Cell Level– docks with cell membrane

• Viral RNA – released into cytoplasm – production new viral proteins/ genetic material

• New viral genomes– rapidly coated in protein – create cores

Copyright: Russell Kightley Media, Australia

Ebola Pathogenesis, cont

• Viral cores – stack up in cell– migrate to the cell surface– produce trans-membrane proteins – push through cell surface– become enveloped by cell membrane

• ssRNA- Genome Mutations – capable of rapid mutation– very adaptable to evade host defenses and environmental change

• Theory– virus evolved to occupy special niches in the wild

Proteins

Clinical Observations

• Incubation period: 2-21 days

• Stage I (unspecific): -Extreme asthenia (body weakness) -diarrhea, nausea and vomiting, anorexia abdominal pain - headaches - arthralgia (neuralgic pain in joints) - myalgia (muscular pain or tenderness), back pain - mucosal redness of the oral cavity, dysphagia (difficulty in

swallowing) - conjunctivitis. - rash all over body except in face

** If the patients don’t recover gradually at this point, there is a high probability that the disease will progress to the second phase, resulting in complications which eventually lead to death (Mupapa et al., 1999).

• Stage II (Specific): - Hemorrhage - neuropsychiatric abnormalities - anuria (the absence of urine formation) - hiccups - tachypnea (rapid breathing).

** Patients who progressed to phase two almost always die. (Ndambi et al., 1999)

• Late Complications: -Arthralgia (joint pain) - ocular diseases (ocular pain, photophobia and hyperlacrimation) - hearing loss - unilateral orchitis( inflammation of one or both of the testes) ** These conditions are usually relieved with the treatment of 1%

atropine and steroids

Clinical Observations

Symptoms and Diagnostic Tests

• Early symptoms– muscle aches, fever, vomiting– red eyes, skin rash, diarrhea, stomach pain

• Acute symptoms

– bleeding/hemorrhaging from skin, orifices, internal organs

• Early Diagnosis • very difficult• signs & symptoms very similar to other infections

• Laboratory Test • PCR detection

• ELISA (enzyme-linked immuno-absorbant) assay

Treatment

• No Standard Treatment available

• Patients receive supportive therapy• treating complicating infections • balancing patient’s fluids and electrolytes• maintaining oxygen status and blood pressure

Prevention

• No vaccines!

• Patients are isolated

• Medical Staff Training – western sanitation practices

• intake• care during stay• after patient dies

• Infection-control Measures– complete equipment and area sterilization

Prevention

After DeathVirus contagious in fluids for days

• Burial use extreme caution

– handling and transport

– cultural practices/ religious belief

– incinerate all waste !!!!

Controlling the spread of Ebola

• a. Hospitals must follow precautionary methods, such as:  1.      wearing gloves 2.      isolating infected individuals 3.      practicing nurse barrier techniques 4.      proper sterilization and disposal of all equipment• b.  Burials must be done correctly 1.      no washing or touching carcass 2.      put into body bags and bury outside city• c. Report any questionable illness to officials                   

Ebola Epidemiology

• Reservoirs in Nature– largely unknown– possibly infected animals (primates?)

• Transmission – direct contact blood/secretions of infected person– possible airborne (Reston primate facility)

• Onset of illness abrupt– incubation period: 2 to 21 days – infections are acute and mostly deadly

Latest Morbidity and Mortality Reports

• Ebola-Reston Virus Infection Among Quarantined Nonhuman Primates -- Texas, 1996

– report describes death and blood testing of cynomolgus

monkey imported from the Philippines held in a private quarantine facility in Texas

• Outbreak of Ebola Hemorrhagic Fever ---Uganda, August 2000--January 2001

– report describes surveillance and control activities related to the EHF outbreak

– presents preliminary clinical and epidemiologic findings

Current Basic Research• The assembly of Ebola virus nucleocapsid requires virion-

associated proteins 35 and 24 and posttranslational modification of nucleoprotein

• Report describes distinct VP35 and VP24 proteins mechanism of regulation for filovirus assembly

• suggests new approaches for viral therapies and vaccines for Ebola and related viruses

• Detection of antibodies against the four subtypes of Ebola virus in sera from any species using a novel antibody-phage indicator assay

• assesses the presence of specific antibodies in serum • describes development of a novel assay for the detection of

seroconversion irrespective of Ebola virus subtype or animal species

Bioterrorism

• Since the September 11 bombings in the United States, the locality of this virus has become less isolated as the threat of bioterrorism looms large.

• The Ebola virus is now on the “A” list for hopeful vaccination development.

• Experiments have even been formed to show how Ebola can be used as a bioterror agent.

References• Reemergence of Ebola Virus in Africa; Anthony Sanchez et al,EID Volume 1 * Number 3 July-September 1995

http://www.cdc.gov/ncidod/EID/vol1no3/sanchez.htm

• Viral Hemorrhagic Fever, Healthlink, Medical College of Wisconsin, 2000 http://healthlink.mcw.edu/article/955159073.html

• Isolation and Phylogenetic Characterization of Ebola Viruses Causing Different Outbreaks in GabonEmerging Infectious Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention ,February 5, 1997 http://www.cdc.gov/ncidod/EID/vol3no1/courbot2.htm

• Hemorrhagic fevers; Julia Barrett, Gale Encyclopedia of Medicine, Gale Research, 1999 http://www.findarticles.com/cf_dls/g2601/0006/2601000652/p1/article.jhtm

lKey Issues in the Prevention and Control of Viral Hemorrhagic Fevers Clarence J.Peters, MD, Special Pathogens Branch/Division of Viral and Rickettsial Diseases, National Center for Infectious Diseases/Centers for Disease Control and Prevention, 1997 http://www.cdc.gov/od/ohs/sympsium/symp43.htm

• Scientific Stock Images Library; Russell Kightley Media,Australia http://www.rkm.com.au/imagelibrary/index.html

• Outbreak of Ebola Hemorrhagic Fever ---Uganda, August 2000--January 2001,Morbidity and Mortality Weekly Report, Vol 50, No 05;73, 02/09/2001 / 50(05);73-7 http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5005a1.htm

• Ebola-Reston Virus Infection Among Quarantined Nonhuman Primates -- Texas, 1996 Morbidity and Mortality Weekly Report, Vol 45, No 15;314  ,April 19, 1996 / 45(15);314-316

http://www.cdc.gov/mmwr/preview/mmwrhtml/00040920.htmThe assembly of Ebola virus nucleocapsid requires virion-associated proteins 35 and 24 and posttranslational modification of nucleoprotein, Huang Y et al, Mol Cell. 2002 Aug;10(2):307-16. PMID: 12191476 [PubMed - indexed for MEDLINE] http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12191476&dopt=Abstract

Detection of antibodies against the four subtypes of ebola virus in sera from any species using a novel antibody-phage indicator assay.; Meissner F et al , PMID: 1235035http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12350354&dopt=Abstract