Emerging arboviruses Flashcards
How could an emerging infectious disease arise?
-New infection (evolution of existing)
-Re emerging of known infections
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What is an EID?
Has increased over last 20 years and could increase in near future
What contributes to a vector borne EID?
- Climate change
- Economic change
- Public health issues
- Poverty
- Change in water supplies
- Change in human susceptibility
- Change in vectoral competency
What are reasons why elimination programmes to get rid of vector borne diseases may have failed?
- Diversion of financial support (no longer became profitable)
- Loss of public health infrastructure (e.g. closing down of emergency treatment centres for ebola)
- Reliance on quick fixes such as drugs and insecticides.
Three examples of arbovirus vectors
Mosquitoes, ticks, sandflies
What is the genome size for the most medically important arboviruses?
11-12 kilo bases
What type of RNA virus is the bunyaviridae family? How is it translated into proteins?
Is a negative sense RNA virus so must form a positive strand before being translated.
What type of RNA virus is the flavivirus family? How is it translated into proteins?
Positive sense RNA. Can be directly translated into proteins by the host ribosome.
What is the extrinsic incubation period?
Time taken by an organism to complete its development in the intermediate host
Describe the structure of flaviviruses. Example?
Enveloped, single strand RNA. Zika.
What proportion of the world is at risk of dengue?
1/3
What is the leading cause of morbidity and mortality in the tropics and subtropics?
Dengue
When did dengue emerge as a worldwide problem?
1950s
What are the serotypes of dengue?
DENV1-4
How many people are affected per year with dengue?
400 m
How has dengue increased in incidence from 1950 to 2013?
<1000 cases per year 1950, >3m cases per year 2013.
Where is mainly endemic for YFV and how many cases and deaths are there?
Mainly in Africa.
60,000 deaths/year
200,000 cases
How is yellow fever prevented?
Live attenuated vaccine.
When was the most recent YFV outbreak?
2016, shortfall in vaccine supply to deal with outbreak
Where else is YFV currently emerging and why?
China, previously absent in asia. Due to aegypti vector presence and large pop exchange between endemic African regions and china
Where have recent outbreaks of zika occurred post 2007?
South America, Asia, Pacific islands
Why is zika importnat?
Sexual transmission, microcephaly, following spread of CHIKV and DENV into southern USA.
Which mosquito transmits jap enceph?
Culex tritaeniorhynchus
What are the zoonotic reservoirs of jap enceph?
Pigs, cattle egrets, pond herrings
HOw many countries are endemic for jap enceph? How many people are at risk?
24
3 billion
When did outbreaks of west nile virus occur and where?
Europe and America in late 1990s
How has west nile virus been maintained (enzoonotically)?
Cycle between mosquitoes and susceptible birds.
Describe epidemiology of usutu virus.
Similar to west nile. Outbreaks in Europe (cases in Italy, Spain, serological evidence in UK) and America.
What are the two encephalitis viruses?
St louis, la crosse.
How is st louis encephalitis maintained?
cycle betwen culex pipiens and birds
How is la crosse ncephalitis maintained?
Aedes mosquito and vertebrate cycle e.g. chipmunks and squirrels also vertical transmission between mosquito and eggs.
Where is endemic for tick borne encephalitis? What is the main vector. What are the main hosts.
Europe, soviet union, Asia. Hard tick. Rodents mainly, humans are accidental hosts.
WHere was powassan isolated and where are cases reported? What might be a zoonotic reservoir?
Canada and Russia. Deer.
What are alpha viruses?
Positive sense ssRNA virus. Enveloped.
Where were outbreaks of CHIKV and also where are they now?
Africa, Asia, Europe, India, Pacific islands, also now most of america
WHich recent event may have caused widespread CHIKV?
Mutation in glycoprotein 1 (at residue 266) which allows A albopictus to transmit.
What is the vector for mayaro and in which people does it commonly occur?
Haemogoggus and in people in contact with humid tropical forests.
What are thought to be the primary vectors for o’nyong’nyong in East Africa?
Anopheles fenestus and gambiae
Where is semliki forest virus found? What are the hosts? What does it cause?
Africa, asia, southern europe.
Wide range-rodents, domestic animals and primates
Lethal encephalitis in rodents, mainly asymptomatic in humans
Which mosquito spp involved in zoonotic cycle for equine enceph? Waht are the types?
Culex. Eastern and western and venezuelan viruses
Give two examples of bunyaviruses. How are they thought to be spreaD?
Crimean congo haemorrhagic fever and rift valley fever. Ticks and mosq respectively.
Whats the vector for oropouche?
Midges
Why may climate change increase arboviral transmission?
Decreases extrinsic incubaiton period. Increased precipitation increased mosquito range.
