Communicable Diseases and Infection Control

Communicable Diseases

• Communicable diseases are illnesses caused by infectious agents or their products that can be transmitted from an infected person, animal, or inanimate reservoir to a susceptible host.
• Infection control requires both individual and community measures.

R-naught (R0)

• R0 is the basic reproduction number, which measures the transmissibility of infectious agents.
• R0 indicates if a disease will spread or decline within a community and how far and how rapidly transmission will occur.
• R0 values:
  • Less than 1: the disease will not spread and will eventually die out.
  • 1: the disease will remain stable in the community but will not cause an epidemic.
  • Greater than 1: the disease will spread and may cause an epidemic.

Control of Communicable Diseases

• Mastering infection control requires a thorough understanding of various infectious diseases.
• Disrupting the propagation of an infectious disease outbreak often only requires understanding how it is transmitted.

HIV/AIDS

• HIV is a retrovirus that infects various cells of the immune system.
• HIV is transmitted through sexual contact, exposure to blood and blood products, childbirth, and breastfeeding.
• Prevention strategies:
  • Education, awareness, and health promotion
  • Post-exposure prophylaxis (chemoprevention)
  • Building health care infrastructure and capacity globally
  • Preventing infected mothers from transmitting the disease to their babies during delivery or through breastfeeding
  • Screening blood/transplant organs of donors
  • Safe sex
• Primary prevention of perinatal transmission:
  • Counseling and testing of pregnant women
  • Adhering to HIV treatment regimen throughout pregnancy and childbirth
  • Giving antiretroviral prophylaxis to the baby after birth
• Post-exposure prophylaxis (PEP):
  • Taking medicine to prevent HIV after exposure (e.g., needle stick injuries)
  • Must be started within 72 hours after exposure and taken daily for 28 days
• Secondary prevention:
  • HIV testing and strengthening local surveillance
  • Improving early diagnosis and access to care
• Tertiary prevention:
  • Treatment with highly active antiretroviral therapy (HAART) or antiretroviral therapy (ART)

Tuberculosis (TB)

• Caused by Mycobacteria (M. tuberculosis in humans and M. bovis in cattle)
• Spread through airborne droplets from people with pulmonary or laryngeal TB
• Stages of TB:
  • Primary TB (exposure): when a person has been in contact with someone who has TB
  • Latent TB infection: the disease remains in a quiet (dormant) state, but never resolves completely
  • TB disease: the person has signs and symptoms of an active infection
• TB interplay of the host and the organism during the initial infection is influenced by multiple factors, including age, immune status, amount of inoculum, nutritional status, and comorbidities
• Untreated, about half of the patients with active TB will die of the disease within 2 years, but modern chemotherapy almost always results in a cure

Malaria

• Primary prevention:
  • Strengthened vector control activities
  • Use of insecticide-impregnated bed nets and curtains, residual house spraying
• Secondary prevention:
  • Case finding
  • Early diagnosis
  • Prompt malaria diagnosis: rapid diagnostic tests (RDTs)
  • Confirmation of diagnosis is by demonstrating malaria parasites on blood smears
• Tertiary prevention:
  • Treatment with combination therapy to reduce resistance
  • Treatment regimens vary by region, depending on drug resistance patterns and potential drug options

This quiz covers the basics of communicable diseases, including their causes, transmission, and control measures. Learn about infection control and the importance of individual and community measures.