Unit 9: Unit 9: Diseases And Immunity — Short Questions

These are the communicable diseases, can spread from person to person or from the environment to person. For example viral infection, bacterial infection and fungal infections etc.

An infectious disease that is naturally transmitted from animals to humans is called zoonotic disease.

Examples Examples of zoonosis include:

a- Anthrax
Introduction: It is caused by the bacterium Bacillus anthracis. The infection site may be skin, lungs or digestive system.
Transmission: Anthrax is transmitted to humans through contact with contaminated animal products (e.g., hides, wool). Usually, anthrax bacteria enter the body through a wound in the skin, by eating contaminated meat or inhaling the spores of bacteria.

b- Bird Flu (Avian Influenza)
Introduction: It is caused by influenza A virus. The infection sites include nose, throat and lungs.
Transmission: Humans get bird flu through close contact with infected birds.

i. Respiratory Allergies (Hay fever, Asthma)
ii. Skin allergies (eczema, contact dermatitis)
iii. Food allergies (common food allergies)
iv. Insect sting allergies (venom allergies)
v. Drug allergies (common drug allergies)

Innate immunity This type of immunity is acquired during life time. It includes the first line of defence and second line of defence.

Acquired immunity It is acquired during life time. It includes the third line of defence.

Skin provides a first line of defence. Skin serves as a physical barrier to pathogens. In addition, the oil and sweat glands present in skin inhibit the growth of many microbes.

Mucous Mucous membranes are epithelial tissues that protect the interior surfaces of the body e.g., respiratory and digestive systems, the urethra. Mucous membranes secrete mucus that traps pathogens.

Definition Non-infectious disease are not caused by pathogens and cannot spread from person to person.

Types
These include:
(i) Physiological diseases (e.g., type 2 diabetes, cancer)
(ii) Genetic disorders (e.g., sickle cell anemia, colour blindness)
(iii) Autoimmune diseases (e.g., type 1 diabetes, rheumatoid arthritis)
(iv) Nutritional deficiency diseases (e.g., scurvy, rickets)
(v) Environmental diseases (e.g., lung cancer from smoking, skin cancer from UV rays)
(vi) Degenerative diseases (e.g., osteoarthritis, Alzheimer's disease)
(vii) Psychological disorders (e.g., anxiety disorders, depression)

(a) Disease and illness

Disease refers to a specific medical condition diagnosed by a physician. A disease is an objective abnormality.

Illness encompasses the patient's subjective experience of being unwell, including emotional and social factors. Illness is the individual's subjective perception of that abnormality.

(b) Infectious and non-infectious diseases

Infectious Diseases Infectious diseases can spread from person to person or from animals to people. An infection occurs when a pathogen enters and multiplies inside a person's body causing disease. Infectious diseases are often preventable with vaccines.

Non-infectious Diseases Non-infectious diseases are not caused by pathogens and cannot spread from person to person. Non-infectious caused by a variety of other circumstantial factors. Infectious diseases can be prevented through lifestyle changes or genetic factors.

(c) Vector and pathogen

Vector Vector is an organism that carries and transmits a pathogen from one host to another without becoming sick itself. e.g., mosquito can act as vector for malarial parasite (plasmodium) transmitting it to humans.

Pathogen A pathogen is a disease causing organism, such as bacteria, viruses, fungi or parasites that can cause infection and illness.

(d) Acute and chronic diseases

Acute Short-term diseases that resolve on their own or with treatment (e.g., pneumonia).

Chronic Long-term diseases that persist or worsen over time (e.g., diabetes).

Types of diseases

According to duration Chronic disease | Acute disease

According to reasons Chronic disease → infectious disease → Bacterial → Physiological → Genetic → Autoimmune → Nutritional → Environmental → Degenerative → Psychological
Acute disease → Non-infectious disease

Symptoms Symptoms of allergic reactions vary depending on the individual and the allergen, but may include:
a. Respiratory issues (congestion, sneezing, coughing)
b. Skin problems (hives, itching, rashes)
c. Gastrointestinal issues (nausea, diarrhoea)

Causes of Allergies
Common causes of allergies include:
1. Genetics: Family history and genetic predisposition
2. Environmental Factors: Exposure to allergens at a young age, hygiene hypothesis.
3. Imbalanced Gut Microbiome: Alterations in the gut flora.
4. Overactive Immune System: Hyperactive immune response.
5. Leaky Gut Syndrome: Intestinal permeability allowing allergens to pass through it.

Allergens can be

• Airborne: Pollen, dust mites, mold
• Food: Peanuts, tree nuts, milk, eggs, fish, shellfish
• Insect Stings: Bee, wasp, hornet, yellow jacket
• Medications: Antibiotics, nonsteroidal anti-inflammatory drugs (NSAIDs).
• Plants: Poison ivy, oak
• Latex: Gloves, balloons
• Pets: Dog, cat, bird
• Household Chemicals: Cleaners, fragrances, cosmetics

With more people living in dense conditions, there is more frequent contact between more individuals, allowing disease transmission to easily occur.

Genetic variations can increase the risk of non-infectious diseases primarily by affecting critical bodily functions and structures, such as immune system regulation, cell growth and metabolism.

People develop allergies due to a mix of genetic predisposition (family history) and environmental triggers, where an overactive immune system mistakes harmless substance (allergos) for threats upon re-exposure, with early childhood hygiene, infection hormonal changes and new exposures all influencing this complex interplay.