CIE AS/A Level Biology -10.1 Infectious diseases- Study Notes- New Syllabus
CIE AS/A Level Biology -10.1 Infectious diseases- Study Notes- New Syllabus
Ace A level Biology Exam with CIE AS/A Level Biology -10.1 Infectious diseases- Study Notes- New Syllabus
Key Concepts:
- state that infectious diseases are caused by pathogens and are transmissible
- state the name and type of pathogen that causes each of the following diseases:
• cholera – caused by the bacterium Vibrio cholerae
• malaria – caused by the protoctists Plasmodium falciparum, Plasmodium malariae, Plasmodium ovale and Plasmodium vivax
• tuberculosis (TB) – caused by the bacteria Mycobacterium tuberculosis and Mycobacterium bovis
• HIV/AIDS – caused by the human immunodeficiency virus
(HIV) - explain how cholera, malaria, TB and HIV are transmitted
- discuss the biological, social and economic factors that need to be considered in the prevention and control of cholera, malaria, TB and HIV (details of the life cycle of the malarial parasite are not expected)
Infectious Diseases
🌱 Overview
Infectious diseases are illnesses caused by pathogens and can be transmitted from one individual to another. They affect humans, animals, and plants.
🔬 Key Points
Pathogens: Microorganisms that cause disease, including:
- Bacteria (e.g., Salmonella, Mycobacterium tuberculosis)
- Viruses (e.g., Influenza virus, HIV)
- Fungi (e.g., Candida species)
- Protozoa (e.g., Plasmodium causing malaria)
Transmissible: Infectious diseases can spread by:
- Direct contact: touching an infected person
- Airborne transmission: inhaling droplets from coughs/sneezes
- Contaminated food or water
- Vectors: animals or insects transmitting pathogens (e.g., mosquitoes)
📊 Summary Table: Infectious vs Non-infectious Diseases
| Feature | Infectious Diseases | Non-infectious Diseases |
|---|---|---|
| Cause | Pathogens (microorganisms) | Genetic, lifestyle, or environmental factors |
| Transmission | Transmissible | Not transmissible |
| Examples | Influenza, Malaria, Tuberculosis | Diabetes, Asthma, Cancer |
– All infectious diseases are caused by pathogens.
– They are capable of spreading between individuals, directly or indirectly.
– Understanding transmission is essential for prevention and control.
Pathogens Causing Specific Infectious Diseases
🌱 Overview
Each infectious disease is caused by a specific pathogen, which may be a bacterium, protoctist, or virus.
🔬 List of Diseases, Pathogens, and Types
| Disease | Pathogen Name | Type of Pathogen |
|---|---|---|
| Cholera | Vibrio cholerae | Bacterium |
| Malaria | Plasmodium falciparum, P. malariae, P. ovale, P. vivax | Protoctist |
| Tuberculosis (TB) | Mycobacterium tuberculosis, M. bovis | Bacteria |
| HIV/AIDS | Human Immunodeficiency Virus (HIV) | Virus |
– Bacteria: Single-celled prokaryotes, often treated with antibiotics.
– Protoctists: Single-celled eukaryotes (like Plasmodium) that may require specific drug treatments.
– Viruses: Non-cellular, replicate inside host cells; treated with antivirals, not antibiotics.
Transmission of Specific Infectious Diseases
🌱 Overview
Each infectious disease spreads via a specific mode of transmission, which is important for prevention and control.
1. Cholera
Pathogen: Vibrio cholerae (bacterium)
Mode of Transmission:
- Fecal–oral route → ingestion of contaminated water or food
- Poor sanitation and hygiene increase risk
2. Malaria
Pathogen: Plasmodium species (protoctist)
Mode of Transmission:
- Vector-borne transmission via female Anopheles mosquitoes
- Mosquito injects sporozoites into human bloodstream while feeding
3. Tuberculosis (TB)
Pathogen: Mycobacterium tuberculosis / M. bovis (bacteria)
Mode of Transmission:
- Airborne transmission → inhalation of droplets from coughs or sneezes of an infected person
- Close, prolonged contact increases risk
4. HIV/AIDS
Pathogen: Human Immunodeficiency Virus (HIV)
Mode of Transmission:
- Direct contact with infected body fluids: blood, semen, vaginal fluids, breast milk
- Common routes: unprotected sexual contact, blood transfusions, sharing needles, mother-to-child during pregnancy/breastfeeding
📊 Summary Table: Transmission Modes
| Disease | Pathogen Type | Mode of Transmission |
|---|---|---|
| Cholera | Bacterium | Contaminated water/food (fecal–oral) |
| Malaria | Protoctist | Mosquito bite (vector-borne) |
| Tuberculosis | Bacteria | Airborne droplets |
| HIV/AIDS | Virus | Body fluids (sexual, blood, mother-to-child) |
– Knowing the mode of transmission helps in preventing the spread.
– Cholera and TB → hygiene and sanitation, clean water, masks in TB outbreaks.
– Malaria → mosquito control (nets, repellents).
– HIV → safe sexual practices, screening of blood, avoiding needle sharing.
Prevention and Control of Infectious Diseases
🌱 Overview
Effective prevention and control of cholera, malaria, TB, and HIV requires consideration of biological, social, and economic factors. These factors influence disease spread, susceptibility, and access to treatment.
🔬 1. Cholera
| Factor | Consideration |
|---|---|
| Biological | Vibrio cholerae spreads via contaminated water; incubation period is short. |
| Social | Poor sanitation, lack of clean water, open defecation, crowded living areas. |
| Economic | Limited infrastructure for clean water supply, sewage systems, and healthcare. |
Prevention & Control Measures: Improve water supply and sanitation, hygiene education, vaccination campaigns, rapid treatment of outbreaks.
🔬 2. Malaria
| Factor | Consideration |
|---|---|
| Biological | Transmission via female Anopheles mosquitoes; seasonality affects prevalence. |
| Social | Use of bed nets, indoor spraying, community awareness, protective clothing. |
| Economic | Cost of mosquito control measures, access to healthcare, affordability of antimalarial drugs. |
Prevention & Control Measures: Mosquito control (nets, insecticides), community education, prompt diagnosis and treatment.
🔬 3. Tuberculosis (TB)
| Factor | Consideration |
|---|---|
| Biological | Airborne bacteria; prolonged exposure increases risk; co-infection with HIV increases susceptibility. |
| Social | Overcrowding, poor ventilation, stigma preventing people from seeking treatment. |
| Economic | Cost of long-term antibiotic treatment, access to healthcare, malnutrition increases susceptibility. |
Prevention & Control Measures: Vaccination (BCG), early detection and treatment, improving living conditions, public awareness campaigns.
🔬 4. HIV/AIDS
| Factor | Consideration |
|---|---|
| Biological | Virus transmitted via body fluids; latent period before symptoms appear. |
| Social | Sexual behaviour, education on safe practices, stigma reducing testing and treatment uptake. |
| Economic | Access to antiretroviral therapy (ART), cost of prevention programs, healthcare infrastructure. |
Prevention & Control Measures: Safe sex education, condom distribution, ART availability, screening of blood products, awareness campaigns.
📊 Summary Table: Key Factors for Prevention and Control
| Disease | Biological Factors | Social Factors | Economic Factors |
|---|---|---|---|
| Cholera | Contaminated water; rapid spread | Sanitation, hygiene, crowding | Infrastructure, clean water supply |
| Malaria | Mosquito vector; seasonal patterns | Bed nets, awareness, protective behaviour | Cost of control, access to treatment |
| TB | Airborne bacteria; co-infections | Overcrowding, stigma | Long-term treatment cost, healthcare access |
| HIV/AIDS | Virus in body fluids | Sexual behaviour, education, stigma | ART cost, healthcare access |
– Prevention must target the pathogen, transmission route, and societal practices.
– Control depends on healthcare access, community participation, and economic resources.
– Considering biological, social, and economic factors together ensures more effective disease management.