Emerging Infectious Agents (5-7) Flashcards
How can you define emerging infectious diseases?
- newly emerging (newly appeared in a population)
- existing but rapidly increasing in incidence or geographic range
- re-emerging/new epidemics of old pathogens
What are the factors attributed to emergence of infectious disease?
Deforestation
Agricultural development
Urbanisation
Habitat fragmentation
Road construction
Air and water pollution
Climate change
Hydrological changes, dam building
Population movement
Drug resistance
Better detection/diagnosis
How has our ability to detect disease improved?
- improved diagnostic sensitivity
- new diagnostics entirely
- improved education/reporting
- modified/improved classification
→ decrease in under-reporting
→ emergence (or re-emergence) or better detection??
How can population movement/migration cause disease emergence?
(population migration or individuals moving)
Migration can replenish susceptibles (more prevalent to disease persistence over emergence)
Movement can introduce the index case of an infection
→ over the last 100 years there has been an increase in travel
How has food production effected emerging infectious diseases?
Since 1940s food production (food industry, land use, agricultural industry) has driven emerging EIDs and zoonotic EIDSs of humans
How has interference with water affected EIDs?
Development and operation of water projects → lots of knock on effects driving emerging infectious diseases
e.g. Cahora Bassa Dam on the Zambezi river in Mozambique
building a dam - changes water flow
downstream → reduced flooding, reduced free standing water, reduced breeding sites
upstream → replaces fast flowing water with large stagnant lake - perfect mosquito breeding site effects on malaria
What’s an example of a re-emerging virus?
Measles
→ droplet and aerosol transmission
→ death rate varies, considerably dependant on healthcare access
→ 1in5 infected develop complications like ear infections, Pneumonia (lung inflammation)
→ cheap and high effective vaccine is available (MMR)
What’s the most common cause of measles outbreaks (re-emergence)?
Vaccine related
→ loss of confidence
→ access to vaccine
→ vaccine scepticism
→ not high enough coverage
What is the main driver of EIDs?
Human behaviour
→ need to globally address human impact, One World/Planetary Health approach
What is the main cause of habitat destruction?
Huge population growth over past 300 years
→ to facilitate the growth we have effected the environment
What is the Biodiversity Intactness Index (BII)?
Estimates how much originally present biodiversity remains on average across the terrestrial ecological communities within a region (decreasing everywhere)
What is the global living Planet Index?
Average abundance of 20,811 populations representing 4,392 species monitored across the globe
→ declined by 68% from 1970 - 2016
Which threatened wildlife species share more viruses with humans?
Wildlife species with population reductions owing to exploitation and loss of habitat
→ encroachment into the habitats of wild species brings them into contact with humans, pets and farmed animals
What is a zoonosis?
Any disease or infection that is naturally transmissible from vertebrate animals to humans
animal host → human (called a ‘spillover’ event)
What are animal reservoirs of human disease?
Population of species with disease that can spread to humans
e.g. birds - influenza, primates - HIV, bats - rabies, ebola, coronaviruses (high priority so over-represented in literature)
Reservoirs with multiple species → control and intervention more difficult
Reservoir species had faster life history characteristics i.e. rodents live shorter/reproduce more, mammals live longer, reproduce less
What infections are bats a host of?
All pathogens that bats were a reservoir of were viruses
including; coronaviruses, Ebola, rabies, chikungunya
What is the principle cause of the AIDS pandemic?
Both Human Immunodeficiency Viruses (HIV) are the result of cross-species transmission of simian immunodeficiency viruses (SIVs) naturally infecting African primates
→ one transmission event involving SIVcpz from chimpanzees in Cameroon gave rise to HIV-! group M - the principle cause of the AIDS pandemic
→ contacts were likely caused by hunting/eating chimpanzees
Why is there continual Ebola incidence?
Frequent ‘spillover’ events from wild species population
→ bats are the natural reservoir of infection
→ constant emergence
What is the reservoir species for Middle East Respiratory Syndrome (MERS)?
MERS-Cov originated in bats, crossed to dromedary camels (intermediate host)
→ camels are now a reservoir species and requires for persistence as human-human transmission is low
→ acquire zoonotic MERS-Cov infection via direct contact with the animal, droplets or fomites e.g. farms, tourism, preparing raw meat, collecting/drinking milk, defecation
What caused the outbreak of MERS-Cov in the Republic of Korea?
The outbreak occurred despite no camels (reservoir species)
→ must have evolved for transmission via human-human
What factors contribute to the re-emergence of disease?
Human activity
→ breakdown of public health measures
→ poverty and social inequality
→ war and famine
→ lack of political will
→ intent to harm (bioterrorism)
Climate and weather
Co-infection
Microbial adaptation and change
What is not a re-emerging disease?
Annual outbreaks or seasonal variation
→ predictable - not emerging#
→ e.g. Scarlet fever
Why does Lyme disease show seasonality?
More present in the summer
→ transmission from infected ticks - more contact in summer
How can Lyme disease be treated and prevented?
Prevention → reduced exposure to ticks bites, no human vaccine
Treatment → doxycycline if caught early
What is the re-emergence of cholera linked to?
Increasing size of populations living in unsanitary conditions
→ infrastructure breakdown, not down to class, can happen to anyone, socio economic class not causative
→ prevented by good sanitation services & waste management
What caused the cholera epidemic in 2010 in Haiti?
Natural disaster - earthquake - broke sanitation infrastructure & aid workers came infected with cholera
→ leading to outbreak
Why is Shigella a re-emerging disease?
Multidrug resistant (MDR) isolates
Is multi-drug resistance included in the category of emerging diseases?
Yes
