Emerging Infectious Disease Flashcards
What is an “Emerging Disease”?
A previously UNKNOWN disease that appears in a population.
OR
A previously known disease that suddenly appears in a NEW population.
What is a “Re-emerging Disease”?
A known disease, previously on the DECLINE that is once again becoming more common and will likely continue to do so.
What were the effects of the re-emergence of Foot and Mouth Disease in the UK in 2001?
- Massive culling of cattle, sheep and pigs to stop disease
- Environmental effects of carcass disposal
- Quarantine of people and animals
- The economic cost of controlling the outbreak
What are the steps in handling an outbreak?
Detection, Investigation and Response
What are the 5 stages of Cross-species disease emergence?
- Agent only in animals
- Single/Primary infection of person or other animal, no transmission (dead end host)
- Infection of people/other animals with a few cycles of transmission
- Spread to people/other animals with sustained transmission among them
- Pathogen exclusive to humans or new animal reservoir
True or False: Most pathogens have multiple host species?
TRUE
Only 37.3% of pathogens only have one known host. The majority of pathogens infect multiple hosts.
Give an example of a stage 2 pathogen and its dead end hosts.
Rabies
- Reservoirs are carnivores and bats
- Dead end hosts are cattle and horses
WNV, EEEV and WEEV
- Reservoirs are birds
- Dead end hosts are humans, horses and dogs
Avian Influenza H5N1
- Reservoirs are waterfowl and poultry
- Dead end hosts are humans
Give an example of a stage 3 pathogen and the “new” hosts.
Mycobacterium bovis
- Transmitted to people from cattle, elk or bison, via respiratory route
- Poor human to human transmission
Nipah Virus
- Transmitted by fruit bats
- Human to human transmission occurs
- Pig to pig transmission occurs
Give an example of a stage 4 pathogen and the “new” hosts.
SARS
- Transmitted from fruit bats
- Now efficient transmission between humans
Swine Influenza H1N1
- Transmitted from swine
- Now efficient transmission between humans
What are a few stage 5 pathogens that are now exclusive to humans, and where did they originate?
HIV/AIDs - originating from non-human primates
Measles - originating from cattle
Dengue - originating from old world primates
Yellow Fever - originating from African primates
What are some Drivers behind pathogen emergence?
Land Use changes
Food and Agricultural systems
Environmental systems
Human behavior
What major factors can lead to a rapid increase in transmission?
- Travel and Tourism
- A person infected with an exotic disease anywhere in the world can be in a major US city within hours (may not even show signs yet)
- Animal-based tourism increases contact with domestic and wildlife species. - Bioterrorism (intentional release)
What are the major determinants of emergence?
- Host susceptibility
- Pathogen type and mutations
- Phylogenetic distance from the reservoir
- Transmission from reservoir
Of the >1400 species of pathogens known to infect humans, what percentage are zoonotic?
61% of pathogens that infect humans are zoonotic
What percentage of emerging diseases in humans are known to be zoonotic?
75% of emerging human diseases are zoonotic