Background of virology II Flashcards
Why is there an increasing trend in size and frequency of emerging disease outbreaks?
Anthropocene -> human presence and activities alter the natural environment in such a way that it is easier for viral infections to (re)emerge and spread
What are the three reasons for increased risk and impact of emerging infectious disease?
- Increased probability of spillover
- Increased probability of spread
- Probability of increased impact
What are the causes of the increased probability of spillover of infectious disease? (3)
- Large scale deforestation
- Animal farming with low biosecurity
- Increasing density of human and animal populations
What are the reasons of increased probability of spread of emerging infectious diseases? (3)
- Global travel and trade
- Megacities with poor infrastructure
- Industrial farming
What are the reasons of a higher probability of increased impact of infectious diseases? (4)
- Ageing populations
- Increased in comorbid population
- Social disparities
- Demographics
Why are viruses particularly adept at adapting to new environments and hosts?
Error-prone viral replication allows them to rapidly mutate and adapt
What are the three options that can follow upon a spillover event from an animal to the human population?
- Dead-end -> no further transmission through humans
- Limited human-to-human transmission
- Transformation into a human-to-human transmissible virus
What is One Health?
Integrated approach that aims to sustainable balance and optimize the health of people, animals and ecosystems
What are two fields of attention when it comes to understanding pre-endemic processes of new diseases?
- Study of re-emergence -> what causes emerging diseases
- Study of response -> early diagnostics, study of host responses, clinical impact of virus, etc.
What is an arbovirus?
Arbo = arthropod-borne -> transmissible via insects
What is an enzoonotic cycle?
Virus circulates among animals with limited chance of spillover to humans
What is a rural epizoonotic cycle?
Virus circulates among domestic animals -> higher chance of spillover to humans
What is an urban epidemic cycle?
Animal vectors and humans living in close proximity, easily allowing spillovers
Which mosquitos are important drivers of arboviruses?
Aedes Aegypti & Aedes albopictus -> tiger mosquitos
What makes Aedes mosquitos particularly good at spreading arboviruses? (4)
- Mostly active during daytime
- Closely related to rural areas
- Important species for endemic arbovirus circulation
- Able to serve as a vector for various viruses
- Increase of habitat of these mosquitos
What are examples of (emerging) arboviruses?
- Dengue
- Chikungunya
- West Nile Virus
- Zikavirus
How much of the world population is at risk of Dengue?
50%
What is the acute systemic illness caused by Dengue virus?
Dengue fever
How many cases of Dengue fever are there worldwide each year?
~90 million
What is a severe/life-threatening complication of Dengue virus infection?
Dengue haemorrhagic fever
How many cases of Dengue haemorrhagic virus are there each year?
~500.000
To which virus family does Dengue belong?
Flaviviruses
What type of genome does Dengue virus have?
+ssRNA (Baltimore group IV)
What is special about the Dengue genome?
It encodes a single polyprotein that is then cleaved into functional viral proteins
How many genotypes of Dengue are there?
4
What is the disadvantage of multiple genotypes of Dengue circulating in the same area?
Second infection with another genotype than the primary infection can lead to immune enhancement of the infection, due to the fact that the antibody response is suboptimal
What is the most severe complication of Chikungunya?
It can cause long-lasting and severely debilitating joint paints
What is the vector of Chikungunya?
Aedes mosquitos
What are the amplifying hosts of Chikungunya? (2)
Birds, rodents
What are the symptoms of Chikungunya? (6)
- Fever
- Joint/muscle pain
- Rash
- Headache
- Nausea
- Fatigue
What is the danger of getting infected with West Nile Virus? Who are most at risk of this?
Severe neurological disease
Elderly most at risk
How many % of the West Nile Virus infections are asymptomatic?
80%
What is the natural host of West Nile Virus?
Birds
West Nile Virus can cause severe disease in humans. Which animals are also at risk of severe disease?
Horses
Why is West Nile Virus spreading rapidly in the United States?
Locally occurring Culex mosquitos are very effective vectors of WNV
Why is it dangerous that Culex mosquitos are able to effectively spread WNV?
They occur almost anywhere in the world
What is a complication of Zikavirus infection during pregnancy?
Microcephaly
To which neurological disease is Zikavirus associated?
Guillain-Barré syndrome
What is the disadvantage of Zikavirus and Dengue occuring in the same area?
Because Zikavirus and Dengue are antigenically very similar, this can lead to immune enhancement
What is the pathofysiological mechanism leading to immune enhancement of DENV/ZIKV? (3 steps)
- Antibodies against one of the virus genotypes do not bind strong enough to other genotypes to neutralize them
- Antibody-virus complexes are internalized by monocytes -> monocyte infected
- New class of cells infected leads to massively increased viral load/disease
Who are especially at risk of immune enhancement of different DENV genotyes and/or ZIKV?
People with low serum titres of neutralizing antibodies
How does ZIKV reach the foetus?
FcnR-mediated transcytosis of maternal IgG that has ZIKV bound to it
