Unit Overview
Infectious Disease
CIE A-Level BiologyΒ· 5 min read π n/a
1. Unit at a Glance
This unit follows a logical arc from foundational concepts to real-world global health challenges. We begin with core terminology: defining what pathogens are and how they spread from host to host. Next, we dive deep into three of the most impactful infectious diseases affecting human populations globally: HIV/AIDS, tuberculosis, and malaria, covering their cause, lifecycle, transmission, and clinical impact. We then explore the use of antibiotics and the growing public health crisis of antibiotic resistance, before concluding with an overview of global strategies to prevent and control infectious disease spread.
Work through the following sub-topics in order to complete the unit:
Pathogens and transmission routes
Introduces the five main classes of pathogens and common modes of transmission between hosts.
β β± 8 min
HIV/AIDS
Covers HIV structure, replication, transmission, progression to AIDS, and prevention/treatment strategies.
β β β± 10 min
Tuberculosis
Explores the cause, transmission, latency, pathogenesis, and control of Mycobacterium tuberculosis infection.
β β β± 7 min
Malaria
Covers the Plasmodium life cycle, vector transmission, symptoms, and control strategies for this parasitic disease.
β β β β± 9 min
Antibiotics and antibiotic resistance
Explains how antibiotics work, how resistance develops and spreads, and strategies to combat resistance.
β β β β± 10 min
Global disease control
Evaluates public health strategies, vaccines, and global initiatives for infectious disease control.
β β β β β± 8 min
2. Common Pitfalls
Wrong move:
Claiming antibiotics are effective against viral infections like HIV.
Why:
Antibiotics target bacterial-specific cellular processes, which viruses do not have.
Correct move:
Remember antibiotics only work against bacterial pathogens, not viruses.
Wrong move:
Stating malaria is transmitted directly from person to person.
Why:
Malaria requires the Anopheles mosquito as an intermediate vector for transmission between humans.
Correct move:
Identify the Anopheles mosquito as the required vector for human malaria infection.
3. Quick Reference Cheatsheet
Key Concept | Summary |
|---|---|
Pathogen classes | Viruses, bacteria, fungi, protoctista, and parasites that cause infectious disease |
HIV target cells | HIV infects and destroys CD4+ helper T cells, crippling the adaptive immune system |
TB latency | Mycobacterium tuberculosis can remain latent in host lungs for decades before reactivating |
Plasmodium hosts | Plasmodium requires two hosts: Anopheles mosquito (vector) and human for its full life cycle |
Antibiotic resistance origin | Resistance arises from random mutations, then spreads via natural selection and gene transfer |
Herd immunity threshold | : Proportion of immune population needed to stop an epidemic |
What's Next
Begin your study of this unit with the first sub-topic on pathogens and transmission routes to build your foundational knowledge. After you complete all sub-topics in this unit on Infectious Disease, you can move on to the next unit covering the mammalian gaseous exchange system.