ICL 1.1: Zoonotic Viruses I Flashcards
what is an emerging virus?
it’s a causative agent of a new or previously unrecognized infection
this is NOT just a virus that we haven’t heard about that shows up somewhere, it could also be a virus that is showing up in a geographically new area
they are infections that have recently appeared within a population or those whose incidence or geographic range is rapidly increasing or threatens to increase in the near future
what could cause an emerging virus to come into existence?
- expanded host range
- transmission from wild/domesticated animals to humans (zoonosis)
- cross-species infection may establish new virus in the population
in what facilities are viruses studied?
special high containment laboratories are required to study viruses or test patient samples
this is what makes research so slow because you have to work in special containment labs so that the researchers are safe and the bug doesn’t escape which takes lots of time and money
which viruses are BSL-3?
BLS = biosafety level
- West Nile virus
- Chikungunya virus
which viruses are BSL-4?
Ebola
what are zoonoses?
infections that can be transmitted to humans from animals
what are the two main ways through which zooneses are transmitted?
- arthropods –> often through blood meals like with mosquitos
- vertebrates –> bites, body fluids, inhalation, etc.
zooneses = infections that can be transmitted to humans from animals
what is a host?
any species capable of sustained viral replication
so lots of things can be hosts!
what is a natural host/reservoir?
the host in the absence of human intervention
this is the host that you’d see in nature
often times, a virus has multiple reservoir hosts which makes getting rid of the virus tricky
what is a dead end host?
an accidental host that is not important in virus life cycle
the dead end host usually doesn’t further transmit the virus
humans are usually the dead end host! we aren’t part of the cycle; if we all died the virus would still exist and be able to replicate
however, we do usually get the most severe form of the disease
which viruses are arthropod transmitted viruses?
- Yellow fever virus (Flaviviridae)
- Dengue virus (Flaviviridae)
- West Nile virus (Flaviviridae)
- Powassan virus (Flaviviridae)
- St. Louis encephalitis virus (Flaviviridae)
- Eastern equine encephalitis virus (Togaviridae)
- Chikungunya virus (Togaviridae)
- La Crosse virus (Bunyaviridae)
which viruses are rodent transmitted viruses?
- Hantaviruses (Bunyaviridae)
2. Lassa virus and LCMV (Arenaviridae)
which viruses are bat associated viruses?
- Rabies virus (Rhabdoviridae)
- Ebola virus and Marburg virus (Filoviridae)
- Nipah and Hendra viruses (Paramyxoviridae)
- SARS (Coronaviridae)
which viruses have a severe association with hemorrhagic fever?
- Yellow fever virus (Flaviviridae)
- Dengue virus (Flaviviridae)
- Hanataviruses (Bunyaviridae)*
- Lassa virus and LCMV (Arenaviridae)
- Ebola virus and Marburg virus (Filoviridae)
which viruses have a severe association with encephalitis?
- West Nile virus (Flaviviridae)
- Powassan virus (Flaviviridae)*
- St. Louis encephalitis virus (Flaviviridae)
- Eastern equine encephalitis virus (Togaviridae)
- La Crosse virus (Bunyaviridae)
- Rabies virus (Rhabdoviridae)
which viruses have a severe association with respiratory problems?
- Nipah and Hendra viruses (Paramyxoviridae)
2. SARS (Coronaviridae)
which virus has a severe association with arthralgia?
Chikungunya virus (Togaviridae)
what are the severe disease associations of Dengue virus?
- hemorrhagic fever
2. arthralgia
what are the severe disease associations of Powassan virus?
- encephalitis
2. hemorrhagic fever
what are the severe disease associations of Hantaviruses?
- hemorrhagic fever
2. respiratory problems
what are the severe disease associations of the Nipah and Hendra viruses?
- respiratory problems
2. encephalitis
what is a vector?
an animal that delivers a virus
what are arboviruses?
arboviruses = arthropod-born viruses (blood sucking)
arbovirus is a collective term that groups together all the arthropod-borne viruses - it is NOT a virus family!!
there are hundreds of arboviruses
they all infect vertebrates
what is the sequence of transmission with arboviruses?
they are spread by ticks or mosquitos that have the virus
the tick/mosquito then transfers the virus to a vertebra such as humans, monkeys, pigs etc.
how do you control the spread of arboviruses?
best strategy for control is vector control
it’s hard to make a vaccine against the hundreds of different arboviruses so instead you have to do vector control and get rid of the mosquito or tick that’s transmitting all the viruses!
if you cut down on the vectors, you cut down on the risk of transmission!
which 4 virus families are arboviruses?
- togaviridae
- flaviviridae
- bunyaviridae
- reoviridae
what is the structure of the togaviridae virus family?
enveloped, icasahedral (+) sense ssRNA
what is the structure of the flaviviridae virus family?
enveloped, icasahedral (+) sense ssRNA
what is the structure of the bunyaviridae virus family?
enveloped, helical (-) sense, segmented ssRNA
what is the structure of the reoviridae virus family?
naked, icosahedral, segmented dsRNA
what are the common features of arboviral diseases?
- often subclinical
- initial replication in endothelial cells and macrophages/monocyte lineage
- viremia = virus in the blood
- low % infections lead to clinical cases
- not all clinical cases lead to major disease
- probably underdiagnosed
why are arboviral diseases probably underdiagnosed?
they’re usually subclinical so you won’t really develop symptoms and even if you do, it’ll just be a headache or muscle pain
so most people don’t go the hospital because they don’t have severe symptoms which means most viruses are probably under-diagnosed
this makes it really hard to assess how many people have actually been infected/exposed to the virus
what is viremia?
virus in the blood
you don’t always have high levels of viremia which makes it hard for the mosquito to pick up the virus from the blood and then transmit it to another animal
which cells are involved initially in arbovirus replication?
initial replication is in endothelial cells and macrophage/monocyte lineage
this is because these are the cells right at the bite site and the cells that are recruited to the site so they’re the first to get infected!