WEEK 5 - Emerging Infections

Question 1

What does emerging and re-emergin infection mean

Answer 1

Emerging = new, never seen before infections

Re-emerging = infectious disease that was previously controlled or reduced to low levels but are coming back / rising

Question 2

How does emerging infections arise

2 steps

Answer 2

Up to 80% of emerging infections derived from animal sources (zoonotic)

Steps:
1. Pathogen is introduced to a new host population
2. Agent is established + transmitted within new host population
- e.g. interactions between humans and animals

Question 3

How and why a novel pathogen emerges

8 Reasons

Answer 3

Due to pathogen spillover:
1. Increase travel / global spread

2. Human population changes
3. Urbanisation
4. Climate change
5. Consuming wild meat
6. Health inequalities
7. Habitat destruction
8. Vaccination hesitancy

NOTE:
- All these factors determine how quickly pathogen may evolve
- If disease transmits quickly = evolution will happen quickly

Question 4

Increase travel / Global spread

How and why a novel pathogen emerges

Answer 4

• Global connectivity via international travelling, allows spread of disease
• Able to import and export diff. pathogens
• Human migration (permanent move to another area)
• International trade of animals and plants
  
  • may allow spread of disease

Question 5

Human population changes

How and why a novel pathogen emerges

Answer 5

Human population changes
- population increase
- living longer / ageing pop.
- older pop. more susceptible to disease
- AMR (antibiotic use) = selection pressures

Question 6

Urbanisation

How and why a novel pathogen emerges

Answer 6

Urbanisation
- People migrating to areas they previously didn’t reside in (a.ka. urban .expansion)
- e.g. migrating to cities for work
- ↑ novel human-wildlife interactions

- Crowded (closer together) = catalyst for rapid transmission
     - e.g. how mosquito borne disease spread 
     - mosquitos are attracted to human odour (and in urbanised areas pop. is high = hotspot for mosquitos)

• In cities likely to have poor air quality (pollution) = immune system negatively affected = ↑ disease susceptibility
  
  • poor immune response = risk of infection

Question 7

Climate Change

How and why a novel pathogen emerges

Answer 7

Climate change
- moving into wild animal habitats
- changes species range: changes their breeding season, habitats
- causes novel intearctions (e.g. bats migrating to habitats near horses, horses come into contact with humans = spread of disease)
- drought/rain impacts rodent pop. (↑ rain = ↑ access to food) ~ rodents carry virus

Question 8

Vaccination hesitancy

How and why a novel pathogen emerges

Answer 8

Immunity and vaccination
- varies amongst cities
- if live in area that has ↓ vaccrination rate / uptake = ↑ risk of acquring infectiom
- ↓ herd immunity

Question 9

How do novel pathogens become a threat

Answer 9

1. Pathogen MUST have ability for person to person transmission
2. Contact between humans and the animal reservoir
   - common reservoir e.g. dog, monkeys, birds, rats, bats
3. This contact allows expanison of pathogen range

NOTE:
some pathogens only transmit from animal to person but cant transmit from person to person (without animal reservoir)

Question 10

Examples of Infectious Disease

Answer 10

1. Smallpox
   
   • only disease to be radicated worldwide
2. Polio
   
   • has potential to be eradicated, but still have some cases around parts of the world
   • eradicated from the western world
3. Diptheria
   
   • bacterial disease, rare to see in West
4. Dengue fever and Choelra
   
   • bacterial disease associated with water
5. Swine flu 2008
   
   • wasn’t virulent / killing many
6. SARS-coronovirus (COVID
   
   • 1st emerged in 2002 (COVID-1) but this had poor transmission between people
   • 2nd emergence in 2019 (COVID-2) had very good transmission = pandemic
   • COVID-2 could be transmitted before you became symptomatic = had to contain
7. MERS
   
   • Middle eastern COVID
   • Origin was camel, virus moved from camel to humans
8. Ebola
   
   • Emerged from rats or bats
   • humans got into close contact with bats due to urbanisation

Question 11

What might happen in the future and why in terms of emerging infectious diseases

Answer 11

• Improvement in vaccine development
• Better access to sanitation and healthcare
• ↓ inequalities
• ↑ funding for outbreak responses
• Developing universal vaccines

Question 12

3 Example Questions

Answer 12

1. Discuss the factors that contribute to the emergence of novel pathogens. In your answer, provide specific examples of pathogens that have emerged in recent history.
2. Evaluate the role of human activities in the emergence and spread of novel pathogens. How do practices such as urbanization, and global travel contribute to pathogen emergence? Support your answer with examples of recent pathogens that have emerged due to these factors
3. Describe the ecological and environmental changes that contribute to the emergence of novel pathogens. How do shifts in biodiversity, climate change, and habitat disruption create conditions favorable for new diseases? Support your argument with relevant examples