3.3 Epidemiology, Vector-Borne Disease Control & Chronic Disease Prevention

Epidemiology, Vector-Borne Disease Control & Chronic Disease Prevention

Epidemiology and public health surveillance direct population-level nursing interventions across the Caribbean. Managing arboviral outbreaks alongside chronic non-communicable diseases (NCDs) requires registered nurses to apply epidemiological metrics, execute integrated vector management, triage severe arboviral complications, and conduct systematic community screening.

Foundational Epidemiological Principles & Outbreak Investigation

The Four Levels of Prevention

1. Primordial Prevention: Inhibits social, economic, and environmental patterns that elevate disease risk across populations. Examples: national sugar-sweetened beverage taxes, tobacco zoning, clean air legislation, and trans fat bans.
2. Primary Prevention: Specific interventions before disease onset to eliminate exposures and preserve health in susceptible individuals. Examples: childhood vaccinations, insecticide-treated bed nets, municipal water chlorination, and promoting 150 minutes of weekly aerobic exercise.
3. Secondary Prevention: Early detection and prompt clinical intervention in asymptomatic, preclinical stages to arrest progression and limit disability. Examples: cervical Pap smears and Visual Inspection with Acetic Acid (VIA), routine opportunistic blood pressure checks at health centres, fasting blood glucose screenings, and contact tracing.
4. Tertiary Prevention: Interventions applied after clinical disease diagnosis to manage chronic impairments and optimize rehabilitation. Examples: diabetic foot ulcer clinics to prevent amputations, stroke motor rehabilitation, cardiac rehabilitation post-infarction, and palliative symptom control.

Measures of Disease Frequency

• Incidence Rate: The rate at which new cases develop in a susceptible population at risk over a specified time interval: Incidence = (Number of new cases occurring during specified time period / Total population at risk during specified period) × k Incidence measures the risk or velocity of contracting disease, serving as the essential metric for investigating acute outbreaks and evaluating etiologic risk factors.
• Prevalence: The proportion of individuals in a population possessing a specific condition at a point in time or period: Prevalence = (Total existing cases at specified time / Total population at specified time) × k Prevalence measures overall disease burden, guiding primary care staffing, bed capacity, drug procurement, and chronic disease allocation (Prevalence ≈ Incidence × Average Disease Duration).

Outbreak Investigation (10 Steps)

Field investigations follow ten systematic steps: (1) Prepare for fieldwork; (2) Confirm outbreak existence (cases exceed endemic baseline); (3) Verify clinical/lab diagnoses; (4) Define cases (person, place, time); (5) Identify cases and line list; (6) Describe data via Epidemic Curves (differentiating point source from propagated spread); (7) Test analytical hypotheses (Odds Ratios / Relative Risks); (8) Perform environmental/laboratory studies; (9) Implement control measures immediately; (10) Disseminate findings and risk communication.

Caribbean Priority Vector-Borne Diseases: Biology & Containment

Aedes aegypti Biology & Vector Control

Aedes aegypti transmits Dengue, Chikungunya, Zika, and Yellow Fever across CARICOM.

• Breeding & Biting Biology: Breeds in artificial domestic containers (uncovered 55-gallon drums, scrap tires, plastic containers, roof gutters). Diurnal feeder with bimodal biting peaks (early morning and late afternoon). Desiccation-resistant eggs survive on dry container walls up to 12 months, hatching upon water contact.
• Integrated Vector Management (IVM):
  • Environmental Source Reduction ("Search and Destroy"): Weekly scrubbing, emptying, and covering containers; disposing of scrap tires; clearing gutters. This is the most sustainable vector control strategy.
  • Biological & Chemical Control: Larvivorous fish (Gambusia) or BTI bacteria in cisterns; Temephos (Abate) 1% sand in potable water drums; ULV adulticidal fogging during crepuscular flight hours during outbreaks.
  • Personal Protection: DEET repellent (20–30%), window screens, and protective light clothing.

Arboviral Clinical Profiles & Severe Dengue Triaging

• Dengue Virus (DENV 1–4):
  • Febrile Phase (days 2–7): High fever, retro-orbital pain, "breakbone" myalgias, flush, petechiae.
  • Critical Phase (days 3–7, at defervescence): Plasma leakage, pleural effusion, ascites, hemoconcentration (hematocrit rise ≥ 20%), and thrombocytopenia (<100,000/μL), risking Dengue Shock Syndrome.
  • Convalescent Phase: Fluid reabsorption, bradycardia, recovery rash ("islands of white in a sea of red").
  • Severe Dengue Warning Signs (Mandatory Hospitalization): Severe abdominal pain; persistent vomiting (PAHO: three or more episodes in 1 hour, or four or more in 6 hours); fluid accumulation; mucosal bleeding; lethargy/restlessness; hepatomegaly >2 cm; rising hematocrit with falling platelets.
  • Management: Immediate admission; titrated IV isotonic crystalloids (0.9% Normal Saline or Ringer's) monitored via urine output (>0.5–1 mL/kg/h). Strictly avoid NSAIDs (aspirin, ibuprofen) due to hemorrhage risk; use paracetamol exclusively.
• Chikungunya (CHIKV): Acute fever with severe, crippling, bilateral small-joint polyarthralgias ("that which bends up"). Shock is rare, but joint pain can persist for months to years.
• Zika (ZIKV): Mild fever, pruritic maculopapular rash, non-purulent conjunctivitis, and arthralgia. Causes Congenital Zika Syndrome (fetal microcephaly, cerebral calcifications) and Guillain-Barré syndrome. Pregnant women require barrier contraception with exposed partners.
• Malaria (P. falciparum / P. vivax): Transmitted by nocturnal Anopheles mosquitoes. Paroxysms: chills → high fever → sweating. Diagnosis: thick/thin Giemsa blood smears.

Non-Communicable Diseases (NCDs), Screening & Community Health Nursing

NCDs account for >70% of mortality in the Caribbean.

• Screening Protocols:
  • Hypertension: Blood pressure at every visit; confirmed if ≥ 140/90 mmHg on ≥ 2 visits.
  • Type 2 Diabetes: Diagnosed by fasting plasma glucose ≥ 7.0 mmol/L (126 mg/dL) or HbA1c ≥ 6.5%. The American Diabetes Association advises screening adults from age 35, or earlier if overweight with other risk factors.
  • Cervical Cancer: Pap smear, visual inspection with acetic acid (VIA) or WHO-preferred HPV DNA testing, according to the national programme (Section 8.3).
  • Breast & Prostate Cancer: Annual breast exams and mammography from age 40–50. Digital rectal examination (DRE) and shared PSA decision-making from age 40–45 for Afro-Caribbean men.
• Lifestyle Counseling (5 A's): Ask (record risk factors); Advise (clear, personalized guidance); Assess (readiness to change); Assist (action plans and barrier mitigation); Arrange (follow-up and community support).
• CHN Home Visiting: Evaluates domestic sanitation, mosquito breeding, fall risks, medication adherence, and caregiver strain. Pre-visit planning liaises with Community Health Aides (CHAs); in-home phase assesses living conditions and clinical status; post-visit phase coordinates referrals. Prioritizes bed-bound elderly, defaulting TB/HIV clients, uncontrolled diabetics with foot ulcers, and vulnerable neonates.