one health lecture 8- emerging diseases Flashcards
what is the greatest threat to global health?
the spread of uncontrolled epidemics
-Especially those that cross borders.
-Have social and economic impacts
-Ebola in West Africa was an alarm call to highlight this need
-Needed forethought and pre-emptive action
what are the 3 major conclusions from this?
-Response is not enough - preparedness for outbreaks requires increased readiness and building resilient health systems.
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Technologically advanced tools are required to anticipates the emergence and amplification of infectious disease outbreaks.
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New risks in the context of big cities and intense mobility of a globalized world - better public health interventions.
what are the 4 types of emerging diseases?
-Newly emerging
Diseases recognized in humans for the first time
-Re-emerging
Diseases that have historically infected humans and continue to reappear in new locations or as resistant forms
-Deliberately emerging
Diseases associated with intent to harm, includes bioterrorism
-Accidentally emerging
Diseases created by humans that are released unintentionally
what are the 3 risks of emerging diseases?
-Disease Factors
-Human Factors
-Ecological Factors
what are human factors?
-Population growth
-Urbanisation
-Human population movement
-Human travel
- Vector travel
-Hunting
-pasturage practices
-Expanding agriculture
-Deforestation/land development
-Dam construction
what is human travel and its effects?
We can reach any part of the world is less than 24hours.
Travel allows us to carry anything (within reason!) with us.
Includes diseases.
Previously diseases would be more contained and/or take longer to reach a global level – not the case now.
This alone is the BIGGEST reason for an increase in emerging diseases.
what is vector travel?
-As we move around the world we also pick up hitchhikers.
-Vectors can be transported by aircrafts.
-Outbreak of West Nile virus in New York (1999), via mosquitoes (Culex pipiens) from the Middle East – via aircrafts
-Further enhanced survival due to climate changes allowing vectors to survive in areas that they otherwise previously could not.
what is the effect of hunting and pasturage?
-60% of known pathogens of humans have a zoonotic origin.
-75% of EID’s are from zoonotic pathogens.
Wildlife play a key role as reservoirs of diseases.
-Crossing the species barrier is when issues arise.
-Disease adapt and become human-human transmission.
-How pandemics start
what are the biological effects of hunting?
-Traditional hunting in Africa can mean that humans come into close contact with nonhuman primates frequently.
-HIV originated in Africa in the late 1940’s, earliest case known in 1959 in DRC.
-HIV is not a zoonotic disease but was zoonotic in origin.
-SIV (Simian Immunodeficiency Virus) found in nonhuman primates
what are pasturage practises?
-Monoculture practices promote susceptibility to infections.
In developing countries the close proximity of animals and humans causes viruses to merge.
-China, as an example, wildlife trade is illegal, but wild animals are commonly sold in live-animal markets (wet-markets).
-Chinese culture fresh food from wild animals are considered great delicacies, but animal housing conditions are often poor.
-Zoonoses can transmit from animals to food handlers – often the simplest explanation for cross-species contamination
how is SARS- CoV – 2 – Severe Acute Sespiratory Syndrome Coronavirus -2 a human factotr?
-A new strain of coronavirus that was not previously identified in humans before – hence it is often referred to as novel.
Bats are a common host to coronaviruses
-Generalist virus circulating in horseshoe bats – evolutionary analysis - lineage from which SARS CoV 2 emerged has been present in bats for several decades.
-Generalist viruses do not need an intermediate host for evolution but it does help for host switching.
-Pangolins get sick so are not a natural reservoir but could act as transmitters between humans.
deadly addition to EIDs.
Forced us to consider how we interact with each other, and the natural world.
Need for us to adapt quickly.
Devastating wake up call - should force us to think more collectively/globally.
A very strong need to take the whole picture into consideration.
how do extreme climatic events have a relationship with EIDs?
-Clear relationship between environmental characteristics and virus emergence.
-21st century extreme climate events are expected to increase - global climate change
Main events
1-El Niño Southern Oscillation (ENSO)
2-Global warming
what is the El Niño Southern Oscillation (ENSO)?
-Fluctuations in temperature between ocean and atmosphere in the east-central Equatorial Pacific.
-El Niño is the warm phase (La Niña is the cold phase).
-North America in the winter season has higher air temps and wetter than average conditions and drier than average conditions depending on the area.
-Hantavirus pulmonary syndrome (HPS) outbreak in 1999 in Four Corners region of the US linked to ENSO.
1992-3 ENSO increased precipitation, lead to an increase in piñon nuts, food for rodents.
-Lead to an increase in deer mice populations – carriers of HPS.
how does global warming effect?
-Small increase can trigger an explosion of insect populations.
-Insects are known vectors of EIDs.
West Nile virus in New York became more established due to:
-Mild 1998-9 winter
-Dry Spring (1999)
-Reduction in predators (frogs, ladybirds and lacewings)
-Mosquito to bird transmission, established a wildlife reservoir.
how does evolution of viral diseases occur?
Evolution and adaptation happens quickly, especially in viral diseases.
Most are RNA viruses with high mutation rates, rapid evolution and environmental adaptability
Happens through point mutation by recombination and reassortment
HOWEVER…
Genetic evolution of viruses does not seem to be the major cause of virus emergence.
Viruses are more stable within their particular ecological niches.
Human factors are the most potent factors driving disease emergence – it is our fault.
