WEEK 5 - Re-emerging Infections

Question 2

What does emerging and re-emergin infection mean

Answer 2

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 3

List examples of re-emerging infections

6 examples

Answer 3

1. Measles
   - due to ↓ vaccination rates
   - viral disease
   - notifiable disease
2. Polio
   - was on verge of global eradictaion
   - poliovirus (viral)
   - notifiable disease
3. Pertussis (whooping cough)
   - due to vaccine hesitancy
   - bacterial disease
   - notifiable disease
4. Tuberculosis (TB)
   - ↑ of drug resistant strains
   - antibiotic resistance key driver
5. Malaria
6. Cholera
   - due to poor sanitation + breakdowns in water

Question 4

What causes re-emergence

Answer 4

1. Antibiotic Resistance
2. Changes in vaccination rates
3. Global travel
4. Environmental Change
5. Immunocompromised Populations
6. Public Health Breakdown

Question 5

Antibiotic Resistance

A factor contributing to re-emergence

Answer 5

• Overuse / misuse of antibitoics lead to development of resistant bacteria strains
• Resistance makes previously treatble infections harder to treat

Example:
- TB is re-emerging due to MDR and resitant strains

Question 6

Changes in vaccination rates

A factor contributing to re-emergence

Answer 6

• ↓ in vaccine uptake = ↓ vaccination coverage
• Reduction can lead to the return of previously controlled diseases

Example:
- Measles

Question 7

Global travel

A factor contributing to re-emergence

Answer 7

• ↑ International travel and trade of animals / plants can introduce pathogens to new area OR / re-introduce pathogens in areas they were once controlled
• Pop. is increasing = ↑ people live closer together = ↑ risk

Example:
- Ebola
- Zika virus

Question 8

Environmental Change

A factor contributing to re-emergence

Answer 8

• Climate change
• Urbanisation
• Destroying habitats
  - e.g. deforestation and agricultral practices

ALL the above brings humans into closer contact with disease vectors e.g. mosquitos, rats, bats

Example:
- Malaria
- Dengue fever

Question 9

Immunocompromised Populations

A factor contributing to re-emergence

Answer 9

• ↑ in conditions that weaken immune system e.g. use of immunosupressants, HIV and AIDs
• ↑ susceptibility of pop. to infetions that were controlled

Example:
- TB

Question 10

Public Health Breakdown

A factor contributing to re-emergence

Answer 10

• War, natural disasters, crises etc. can disrupt healthcare systems and sanitation

Examples:
- Cholera

Question 11

Measles

Inc. cause, transmission, complications, prevention and current status

Answer 11

Cause: Morbillivirus

Transmission: Air droplets (very contagious)

Complications: Neurological damage, ear damage, pneumonia, encephalitis
- more common in children <5

Prevention: 2 dose MMR vaccination,

Current Status: Despite eliminations in US outbreaks may still occur due to ↓ vaccine / immunisation rates and international travel

NOTE:
- Was a common childhood disease until vaccine introduction

Question 12

Measles: Pathophysiology

Answer 12

The measles virus causes disease by:

1. Infecting the respiratory tract through inhalation of viral droplets
2. Virus replicates in epithelial respiratory cells, damaging the infected cells and triggers release of viral particles
   
   • viral particles are spread via coughing or sneezing
3. The virus then invades the lymphatic system, infecting immune cells (e.g. macrophages, dendritic cells)
   
   • viremia proccess occurs (virus is carried to lymph nodes + spreads through the bloodstream)
4. Virus spreads through bloodstream infecting various tissues (e.g. skin, liver, lungs, brain) = systemic spread
   - hence rash appears over whole body as immune resposne is. targetting infected cells

In summary, measles infects the respiratory tract, spreads through the body, weakens the immune system, and leads to widespread tissue damage and complications

Question 13

Measles: Symptoms

Answer 13

Symptoms appear 7-14 days after exposure

• High fever
• Cough
• Runny nose
• Red, watery eyes (conjunctivitis)
• Blotch rash (appears 3-5 days after symptoms listed above)
  - 1st appears on forehead then spreads down body
  - may appear in mouth
• Hacking cough / sore throat

NOTE:
- may have similarities to chickenpox

Question 14

5 Reasons why measles re-emerged

Answer 14

1. Vaccine hesitancy / decline
   - ↓ in vaccination rates = ↓ vaccination coverage = ↑ in unvaccinated individuals
   - As measles is highly contaigous to achieve herd immunity 95% vaccination coverage is required
   - ↓ in coverage leads to outbreak
   - ↓ due to misinformation (autism) and distrust in vaccine
2. Global travel and Migration
   - international travel allows people to carry measles from one region to another
   - measles can be re-introduced into places that previously eliminated it by travellers
3. Conflict and Displacement
   
   • War can disrupt public health infastructure = ↓ vaccination coverage and lack of access to healthcare
4. Weak Healthcare Systems
   - Some countries lack access to vaccines = low immunisation rates
5. Highly contagious nature of measles
   
   • 9 out of 10 unprotected indivuals that come into contact with infected will contract measles
   • Spreads quickly in communities with ↓ vaccination rates
   • Virus can remain airbone + on surfaces for several hours

Question 15

Polio

Inc. cause, transmission, complications, prevention and current status

Answer 15

Cause: Poliovirus

Transmission:
1. Faecal-oral: virus excreted in faeces + contaminates food or water
2. Oral-oral: virus spread through respiratory droplets
3. Person-person: direct contact with infected faeces or droplets (from cough/sneeze)

Complications:
- Virus may invade CNS causing paralysis, permanent disability and death

Prevention:
- IPV (most commonly used) or OPV vaccine
- Good sanitisation (wash hands, sanitisation facilities)
- Avoid undercooked foods

Question 16

Polio: Pathophysiology

Answer 16

1. Poliovirus enters the GI tract where it replicates in the pharynx and intestines
   
   • it then spreads to lymphoid tissues e.g. tonsils, lymph nodes
   • early stage symptms: sore throat, fever or GI distress
2. Viremia (virus enters blood stream)
   
   • in most cases immune system clears virus out of blood = end of infection (in mild / asymptomatic cases)
   • may develop fever, malaise, muscle aches, flu-like symptoms
3. CNS invasion (1% severe cases)
   
   • Virus is able to cross BBB + invade CNS
   • Virus infects + destroys motor neurons in the spinal cord and brainstem
4. Paralysis and Motor neurone damage
   
   • When motor neurones are damaged this causes paralysis
   • motor neurone destruction is irreverisble = permanent muscle atrophy and loss of voluntary movement
5. Recovery and Post-polio syndrome
   
   • Some indivuals may regain some function weeks/months after infection (incomplete recovery)
   • Years later, survivors may develop post-polio syndrome
     - inc. progressive muscle weakness, fatigue, and joint pain
     - due to the failure of neurons that compensated for the damaged ones
6. Immune response
   - Innate immunity: when infected body innate immune cells (macrophages, dendritic cells) try to contain virus
   - Humoral immunity: IgM and IgG antibodies are produced which neutralise virus preventing spread to CNS
   - Cell-mediated immunity: T-cells target virus-infected cells

Summary: Polio primarily involves the destruction of motor neurons, leading to paralysis. In severe cases, it can affect the respiratory muscles. While recovery is possible, some individuals later develop post-polio syndrome

Question 17

2 Types of Polio

Answer 17

1. Non-paralytic Polio
   - Get flu-like symptoms and stiff neck but NO paralysis
2. Paralytic Polio
   - Occurs when virus infects spinal cord or brainstem = muscle paralysis
   - Can lead to diability

Question 18

Polio: Symptoms

Answer 18

• Flu-like symptoms e.g. fever, sore throat, fatugue, nausea
• Tiredness
• Muscle atrophy
• Headache
• Difficulty breathing
• Limb paralysis

NOTE:
- most cases are asymptomatic (show no symptoms but still shed virus)

Question 19

6 Reasons why polio re-emerged

Answer 19

1. Vaccination gaps
   - due to parents refusal, conflict, poverty, no access
   - recommended vaccination coverage to prevent the reintroduction of the virus is 95%
   - ↓ coverage = ↓ immunisation
   - immunisation requires multiple doses
2. Vaccine-Derived Poliovirus (VDPV)
   - OPV is highly effective vaccine BUT its LIVE ATTENUATED = in rare cases virus can mutate + revert to form that can cause paralysis
   - occurs in under-immunized populations where the weakened virus is able to circulate for long periods.
3. Conflict and War
   
   • can disrupt vaccination campaigns
   • displacement of pop. can spread virus to previoulsy polio free areas
4. Misinfomration and Vaccine hesitancy
   
   • misinformation about vaccines has led to resistance and refusal of vaccination
5. Poor sanitisation and hygiene
   
   • polio virus spreads primarily through contaminated water and food
   • in regions with poor sanitation, the virus can easily be transmitted
6. Surveillance Lapses
   
   • Inadequate disease surveillance can allow polio to spread unnoticed, especially in remote areas

NOTE:
- diff. live attenuated polio vaccine strains can actually cause paralysis = despite being cheaper and being able to be given orally should GIVE INACCTIVATED virus

Question 20

Pertussis (whooping cough)

Inc. cause, transmission, complications, prevention and diagnosis

Answer 20

Cause: Brodtella pertussis (bacterial infection)

Transmission: Respiratory droplets (cough / sneeze)
- incubation period is 4 to 21 days

Complications: pneumonia, seizures, brain damage (lack of O2 due to prolonged coughig), death

Diagnosis: Lab tests e.g. nasopharyngeal swab (check for bacteria), blood tests and PCR

Prevention: DTaP vaccine (multiple dosing in childhood) and Tdap booster (adulthood)

NOTE:
- primarily affects infants + young children (have severe complications)
- BUT can still affect older children + adults

Question 21

Pertussis: Pathophysiology

Answer 21

Bacterial multiplication leads to the development of various virulent factors e.g. toxins, ability to attach to epithelial cells etc.

1. Inhalation of respiratory droplets containing B.pertussis (from infected person cough / sneeze)
2. Bacteria attaches to ciliated airway epithelium + produce toxins e.g. PT (pertussis toxin), TCT, FHA, ACT
3. Bacteria multiplies in respiratory tract causing:
   • Influx of neutrophils
   • Damage to ciliated epithelium due to toxins
   • Mucus hypersecretion due to damage = whooping cough

Toxins affect many immune cells e.g.
- Macrophage – PT inhibits anti-bacterial function = ↓ ability to clear bacteria
- Neutrophil – PT inhibits recruitment to airways, ACT and FHA inhibit phagocytosis
- Dendritic cells – ACT inhbits their maturation + transport to lymph nodes
- T regulatory lymphocytes – FHA stimulates the generation ofFHA-specific Tregs which secreteIL-10, suppressing Th1 immune responses

Question 22

Pertussis: Symptoms

Answer 22

Early Stage:
- cold-like symtpms e.g. runny nise, mild fever, sneezing, mild cough
- most contagious stage
- lasts 1-2 weeks

Later Stage:
- severe coughing fit develops followed by high-pitched ‘whoop’ sound when inhale
- vomitting, exhaustion
- severe cases, broken ribs

Recovery Stage:
- symptoms gradually improve
- coughing fits can last weeks to months

Question 23

Pertussis: Treatment

Answer 23

1. Antibiotics
   
   • used in early stages to ↓ spread
2. Supportive care
   
   • inc. managining sympt. + preventing dehydration
3. Hospitalisation
   
   • necessary for severe cases

Question 24

Pertussis: Virulence factors

7 Factors

Answer 24

1. FHA
   - a surface protein that facilitates bacterial adhesion to airway cilliated epithelial cells
   - allowing bacteria to resist mechanical clearnace by cilliary action
2. Pertussis Toxin (PTx)
   - an endotoxin that disrupts host immune response
   - causes ↑ cAMP production = weakens immune cells allowing bacteria to invade immune system
3. ACT (toxin)
   - converts ATP to cAMP = disrupts immune system
   - creates pores in host cell membrane = lysis + weakened immune response
4. TCT (toxin)
   - fragment of bacterial cell wall that causes damage to cilliated epithelial cells
   - inhibits clearance of mucus + bacteria
   - contributes to coughing sympt.
5. Pertactin
   - outer membrane (OM) protein that prmotes attachment of bacteria to epithelial cells
   - involved in evading immune response
6. Fimbriae
   - Structures on bacteria surface that enhances adhesion to host cell
7. Lipopolysaccharide (LPS)
   - LPS are found on OM + trigger inflammatory response
   - helps bacteria invade immune response

Question 25

6 Reasons why pertussis re-emerged

Answer 25

1. Vaccine decline
   - ↓ vaccination rates = ↓ vaccine coverage
   - lack of access to vaccine
   - vaccine hesitancy
   - conflict affect healthcare
2. Waning immunity
   - immunity provided by vaccine and natural infection wanes over time
   - vaccinated children may become susceptible in adulthood
3. Vaccine composition
   - Switch from wP (whole) to aP (acellular) is associated with ↓ long-term immunity
   - aP vaccine is safer + has less side effects but doesn’t provide broad immunity
4. Genetic & serological change in B. pertussis
   - bacteria evolving due to vaccine pressures
   - developing mutations = can evade immune response
5. Diagnostic improvements
   - better tools = more accurate identification
   - may not be re-emrging but we are detecting more cases due to improvements
6. Asymptomatic carriers
   - Vaccinated individuals (with no sympt.) may still carry + transmit bacteria without = pathogen can still spread in pop.

Question 26

What is the role of the pharmacist

Answer 26

1. Vaccine Advocacy and Administration:
   
   • educating patients about vaccine
     importance, dispelling myths, adress hesitancy
   • administe vaccines and monitor vaccination schedules
2. Public Health Surveillance and Reporting:
   
   • monitoring outbreaks and reporting suspected cases
   • reporting adverse vaccine events / reactions to ensure safety
3. Community Engagement:
   
   • leading health campaigns and outreach programs, especially in underserved areas
   • AIM: ↑ awareness and vaccine coverage
4. Dispensing and Managing Medications:
   - supporting patients during outbreaks with medications and advice
   - supporting patients in post-polio syndrome management
5. Counteracting Misinformation:
   - addressing vaccine hesitancy and correcting misconceptions