Infectious Diseases and Treatment Challenges

• Transmission of HIV in Body Fluids

  HIV (Human Immunodeficiency Virus) is primarily transmitted through certain body fluids. Understanding these transmission mechanisms is crucial for prevention and public health.
• Mechanisms of HIV Transmission:

  1. Sexual Contact
  2. Blood Transmission
  3. Mother-to-Child Transmission
• Sexual Contact


  • Unprotected sexual intercourse (vaginal, anal, or oral) with an infected person
  • Body fluids involved: Semen, vaginal fluids, rectal fluids
• Blood Transmission

  • Sharing needles or syringes (common in intravenous drug use)
  • Blood transfusions (rare in countries with robust screening procedures)
  • Accidental needle sticks (risk for healthcare workers)
• Mother-to-Child Transmission


  • During pregnancy
  • During childbirth
  • Through breastfeeding
  • Body fluids involved: Blood, breast milk
• HIV is not transmitted through casual contact like hugging, shaking hands, or sharing utensils.
• Infection of Lymphocytes by HIV and AIDS

  HIV specifically targets and infects certain types of lymphocytes, leading to a weakened immune system and eventually to AIDS (Acquired Immunodeficiency Syndrome).
• Target Cells of HIV

  • HIV primarily infects CD4+ T lymphocytes (also known as helper T cells)
  • These cells are crucial for coordinating the immune response
• Infection Process of HIV

  • HIV enters the CD4+ T cells
  • Uses the cell's machinery to replicate
  • Kills the infected cells in the process
• Consequences of HIV

  • Gradual reduction in CD4+ T cell count
  • Weakened ability to produce antibodies
  • Compromised ability to fight opportunistic infections
• Progression to AIDS

  • AIDS is diagnosed when CD4+ T cell count falls below a certain level (typically 200 cells/mm³) Or when opportunistic infections occur
• Antibiotics

  Targeting Bacteria, Not Eukaryotes: Antibiotics are like precision weapons in our battle against bacterial infections. They work by targeting specific processes in bacteria that are either absent or different in eukaryotic cells (including human cells)
• Bacterial Targets:

  Antibiotics block processes such as:

  • Cell wall synthesis
  • Protein synthesis
  • DNA replication
  • Metabolic pathways
• Eukaryotic Cell Safety: 


  These processes are either absent or significantly different in eukaryotic cells, making antibiotics generally safe for humans.
• Why Antibiotics Don't Work on Viruses

  Antibiotics are ineffective against viruses for several reasons:

  1. Cellular Structure: Viruses are not cells and lack many of the structures targeted by antibiotics.
  2. Replication Mechanism: Viruses use host cell machinery to replicate, not their own.
  3. Metabolic Processes: Viruses don't have their own metabolism to disrupt.
• Evolution of Antibiotic Resistance


  Antibiotic resistance is a prime example of evolution in action, occurring rapidly in bacterial populations due to their short generation times and large population sizes.
• Process of Resistance Development:


  1. Random genetic mutations occur in bacteria
  2. Some mutations confer antibiotic resistance
  3. Under antibiotic pressure, resistant bacteria survive and reproduce
  4. Resistant traits are passed on to offspring
  5. The resistant population becomes dominant
• Multiresistant Bacteria


  Some bacteria have evolved resistance to multiple antibiotics, making them particularly dangerous. These are often called "superbugs."
• Slowing Resistance:

  To slow the emergence of resistant strains:

  1. Use antibiotics only when necessary
  2. Complete the full course of prescribed antibiotics
  3. Avoid using broad-spectrum antibiotics when narrow-spectrum ones will suffice
  4. Implement proper hygiene and infection control measures
• Nature of Science: New Techniques in Antibiotic Discovery

  The search for new antibiotics has been revolutionized by modern techniques:

  1. Chemical Libraries: Large collections of chemical compounds are screened for antibiotic properties.
  2. High-Throughput Screening: Automated testing of thousands of compounds against bacterial targets.
  3. Genomic Approaches: Using bacterial genome information to identify new antibiotic targets.
• These new techniques are crucial as traditional methods of antibiotic discovery have largely been exhausted, and we desperately need new antibiotics to combat resistant strains.
• Zoonoses


  Infectious Diseases Crossing Species Barriers: Zoonoses are infectious diseases that can transfer from animals to humans. These diseases represent a significant portion of human infectious diseases and can have profound impacts on public health.
• Examples of Zoonoses:

  1. Tuberculosis (TB)
  2. Rabies
  3. Japanese Encephalitis
  4. COVID-19
• Tuberculosis (TB)


  • Caused by Mycobacterium bovis (cattle strain)
  • Transmission: Inhalation of aerosols or ingestion of contaminated milk
• Rabies


  • Caused by Rabies virus
  • Transmission: Bite or scratch from infected animals (commonly dogs, bats)
• Japanese Encephalitis

  • Caused by Japanese encephalitis virus
  • Transmission: Mosquito bite (pigs and birds are reservoir hosts)
• COVID-19


  • Caused by SARS-CoV-2 virus
  • Likely originated in bats, with possible intermediate host
  • Transmission: Respiratory droplets, close contact
• Impact of COVID-19

  COVID-19 serves as a stark reminder of the potential consequences of zoonotic diseases:

  1. Global pandemic
  2. Significant mortality and morbidity
  3. Economic disruption
  4. Social and lifestyle changes