ORGB 423 Lecture Notes - Lecture 5: Myxoma Virus, Chikungunya, Richter Magnitude Scale
12 Jun 2018
School
Department
Course
Professor
MIMM466: Viral Pathogenesis
2018-01-15 LEC 5 Evolving and Emerging Viruses in a Global Perspective
Dr. Anne Gatignol
Will Infectious Diseases be Eradicated in the Near Future?
• 1948: “World has the means to eradicate infectious disease” – US Secretary of State
• 1963: “In 100 years, all major infectious will have disappeared” – WHO
• 1969: “Time to close the book on infectious disease” – US Surgeon
• No eradication (except smallpox in 1979), emergence of new infectious diseases
o E.g. Chikungunya, Ebola, AIDS, Plague, Hendra, Nipah viruses, SARS, MERS, Influenza,
Zika…etc.
• 1996: Fact sheet addressing threat of infectious disease released (Bill Clinton)
• 1997: WHO released global alerts for emerging infectious diseases
Richter scale: classifies different factors by rate of cause of death
• Viruses classified as massively destructive
Where do viruses come from?
• Hosts all come from species evolution
• Viruses come from co-evolution with hosts
• Viruses have evolved by co-speciation together with independent events
o Host transfer, extinction, duplication of viruses due to different events
• All species have some kind of viral RNA transcript
o There are a lot of genetic exchanges that can increase the diversity of species
• Virus evolution: constant change of viral population in the face of selective pressures
o Sources of diversity: mutation, recombination, reassortment, selection
• Emerging virus: causative agent of a new and previously unrecognized infection in a population
o Manifestation of virus evolution
o Result of host-virus interaction on a large scale
Examples of emerging & re-emerging viruses:
Dengue, Ebola, Influenza, HIV, SARS, MERS, Chikungunya, Zika, Hendra/Nipah, (Haantan/Junin/Machupo)
Origin of major human infectious diseases
• Stage 1: agent only occurs in animals, no transmission to humans
• Stage 2: primary infection transmitted from animals, no human-human infection
o E.g. Nipah, Rabies, West Nile
• Stage 3: Limited infection à dissemination from animals to humans, limited dissemination in humans
o E.g. Ebola, Marburg, Monkeypox
• Stage 4: long outbreak à dissemination from animals to humans, human-human transmission
o E.g. Influenza A, dengue, YFV
• Stage 5: only reservoir is humans, possible to eradicate
o E.g. Measles, Mumps, Rubella, Smallpox, HIV
Dynamic Spectrum of Virus-Host Interactions
• Evolving: unstable, unpredictable, reassortment, mutations that increase virus spread, new host
o E.g. smallpox and measles in Native Americans, West-Nile virus old world à new world,
feline à canine parvovirus, influenza
• Resistant: Host cells not susceptible or not permissive, no disease
o E.g. humans not susceptible to rabbitpox myxoma virus
• Stable: Virus and host multiply and both populations survive
Document Summary
2018-01-15 lec 5 evolving and emerging viruses in a global perspective. Chikungunya, ebola, aids, plague, hendra, nipah viruses, sars, mers, influenza, Zika etc: 1996: fact sheet addressing threat of infectious disease released (bill clinton, 1997: who released global alerts for emerging infectious diseases. Richter scale: classifies different factors by rate of cause of death: viruses classified as massively destructive. Dengue, ebola, influenza, hiv, sars, mers, chikungunya, zika, hendra/nipah, (haantan/junin/machupo) Origin of major human infectious diseases: stage 1: agent only occurs in animals, no transmission to humans, stage 2: primary infection transmitted from animals, no human-human infection, e. g. Nipah, rabies, west nile: stage 3: limited infection dissemination from animals to humans, limited dissemination in humans, e. g. Ebola, marburg, monkeypox: stage 4: long outbreak dissemination from animals to humans, human-human transmission, e. g. Influenza a, dengue, yfv: stage 5: only reservoir is humans, possible to eradicate, e. g. Dengue, yfv, marburg, ebola, lassa, junin, h5n1 flu ( etc. )
