10: Infectious Disease - A global picture

Question 1

Definitions:

1. Outbreak
2. Endemic
3. Endemic
4. Pandemic
5. Sporadic

Answer 1

1. Outbreak: When more cases of a disease than expected are recorded in one area
2. Endemic:
   - Outbreak occurring at a predictable rate in a given geographical area/population
   - Usual/expected frequency of disease (steady state)
   - E.g. Chicken pox
3. Epidemic:
   - Unusual occurrence of disease in a community of disease
   - In clear excess of expected occurrence
   - E.g. SARS, Ebola
4. Pandemic:
   - Epidemic that spreads beyond borders of endemic region
   - Worldwide spread of a new infectious disease
   - E.g. The black death, swine flu, COVID-19
5. Sporadic:
   - Irregular outbreaks or disease with no recognisable common source of infection
   - Could be starting point for epidemic in favourable conditions
   - E.g. Polio

Question 2

Control

Answer 2

• Reduction in incidence, prevalence, morbidity or mortality of a disease/infection to a locally acceptable level
• Continued intervention measures required
• E.g. Malaria

Question 3

Elimination

Answer 3

• Reduction of disease/infection to zero in given geographical area
• Continued intervention measures required
• E.g. Measles, polio (eradication target)

Question 4

Eradication

Answer 4

• Permanent reduction of disease/infection to zero globally
• Routine intervention measures no longer required
• E.g. Smallpox

Question 5

Extinctions

Answer 5

• The specific infectious agent no longer exists in nature or laboratory

Question 6

Prevention, diagnosis, treatment barriers/factors

Answer 6

Prevention:

• Vaccination not always available
• Hygiene measures
• Access to clean water, sanitation, nutrition required

Diagnosis:
- Access to suitable facility/timely diagnosis

Treatment:

• Access to medication
• Suitability of dosage form

Question 7

Prevention

Answer 7

• Quarantine – separation of people who have been exposed to a contagious disease
• Isolation – separation of people who are ill with an infectious disease
• Water/sanitation interventions – washing hands, boiling water
• Vector control – residential home spraying

Question 8

Infection control

Answer 8

• Chemoprophylaxis (mass drug administration for treatment/prophylaxis)
• Vaccination
• Physical barriers between host & vectors e.g. Bed nets
• Treatment of infected host

Interventions that affect the agent

• Pesticides/insecticides
• Repellents
• Biological control
• Environmental modification

Question 9

Vaccinations

Answer 9

• Averts ~ 2.5 million child deaths/year (millions more illnesses/disability)
• Equitable health intervention – gender, access
• An additional 1.5 million deaths could be avoided if global vaccination coverage improves

Question 10

Vaccination challenges

Answer 10

• High prices of newer vaccines
• Lack of R & D for better-adapted/required vaccines
• Weak health systems/health worker shortages

More than 30 million children are unimmunised because:

• Vaccines are unavailable
• Health services are poorly provided/inaccessible
• Families are uninformed/misinformed

Question 11

Global vaccine action plan

Answer 11

• The 1st 10-year strategic framework to realise the potential of immunisation (launched in 2005)
  + 2011-2020: Decade of vaccines
• > 1100 individuals in 140 countries from 290 distinct organisations

Vision: A world in which all individuals & communities enjoy lives free from vaccine-preventable diseases

Question 12

Six goals of the global vaccine action plan

Answer 12

1. Immunisation against diphtheria, tetanus & pertussis
2. Measles mortality reduction
3. Rubella elimination
4. Maternal & neonatal tetanus elimination
5. Polio eradication
6. Use of new or underutilised vaccines

Question 13

Measles (Rubeola)

Answer 13

• Infection caused by rubeola virus
• Airborne disease (aerosol transmission)
• There is no specific antiviral therapy for measles - Medical care is supportive & to help relieve symptoms & address complications such as bacterial infections

Measles vaccine

• 2 doses
• 95% effective after 1 dose, 99% effective after 2 doses

Question 14

Herd immunity

Answer 14

• Level of immunity in a population when introduction will typically not lead to spread of disease
• Level required to reach herd immunity depends on how infectious the disease is
  + Measles is one of the most infectious diseases known, so community vaccination coverage levels of 95% are needed

Question 15

Polio eradication process - 1988 - 2020

Answer 15

In 2020 only 2 countries have not eradicated polio – Afghanistan & Pakistan

Question 16

Poverty (LICs)

Answer 16

• Poverty cultivates conditions for disease to spread
• Infectious diseases exacerbate factors contributing to poverty
  + Healthcare costs
  + Time off work/job loss

Question 17

Defining & measuring access to essential drugs (pharmaceutical products & services)

1. Accessibility
2. Availability
3. Acceptability
4. Affordability

Answer 17

1. Accessibility:
   - Location of products & services
   - Location of users
2. Availability:
   - Supply of products & services
   - Demand for products & services
3. Acceptability:
   - Characteristics of products & services
   - Attitudes & expectations of user
4. Affordability:
   - Prices of products & services
   - Income & ability to pay

Question 18

Neglected tropical diseases

Refer to lecture notes

Answer 18

• Diverse group of communicable diseases
• All low-income countries are affected by at least 5 neglected tropical diseases simultaneously
• Worldwide, 149 countries & territories are affected by at least one neglected tropical disease (NTD)
• Many NTDs can cause chronic diseases
• Treatment cost for most NTD mass drug administration programmes is estimated at < 50c/person/year
• Some NTD treatments lack empirical evidence/can be highly toxic
• The WHO developed a roadmap that was meant to officially launch in June 2020 that includes specific disease control targets to control & eliminate NTDs by 2030

Question 19

Impact of COVID-19 on NTDs

Answer 19

COVID-19 has affected implementation of essential health services:

• Suspension of mass treatment interventions
• Delays in health services (diagnosis, treatment)
• Discontinued monitoring, evaluation
• Delays in manufacture, shipment & delivery drugs
• Re-assignment of personnel

Consequences:

• Resurgence of infections
• Increased morbidity/mortality from NTDs
• Delays in reaching public-health goals set for NTDs
• Reduced collection/analysis of epidemiological data

Question 20

Sustainable development goals

Answer 20

• Addresses global challenges in healthcare
• More than just prevention of disease
• Adopted by 189 nations since 2000

Question 21

Example: Global health challenges - Pneumonia

Answer 21

• Pneumonia is the leading cause of mortality in children < 5
• Out-patient treatment (WHO): Amoxicillin 250 – 500 mg bd for 3-5/7 days depending on age & risk
• Child-friendly dosage forms unavailable in many countries
  + Manipulation of adult dosage forms
  + Compromised efficacy, adherence, medicine stability
• The challenge: New ways to reduce pneumonia fatalities through timely, effective treatment of children
  + An affordable, acceptable, readily available, easy access amoxicillin dosage form for children < 5