Diseases are fundamentally defined as conditions that disrupt the normal functioning of the body, leading to specific symptoms and a decline in health. They are broadly classified into two categories: communicable and non-communicable diseases. Communicable diseases, also known as infectious diseases, are those that can be transmitted from one person to another through various agents like bacteria, viruses, fungi, or protozoa. In contrast, non-communicable diseases, such as diabetes or heart conditions, cannot be spread through contact and are often linked to genetic factors, organ malfunctions, or long-term lifestyle choices. Understanding this primary distinction is the first step in studying how diseases affect populations and individuals.
The spread of communicable diseases follows a clear chain, beginning with a causative agent, or pathogen. These pathogens reside in a reservoir, which is often an infected person, and exit their body through portals like saliva or nasal discharge. Transmission to a new, healthy host can occur through multiple routes, including direct physical contact, contaminated food and water, airborne droplets from a sneeze or cough, or through carriers like insects (e.g., mosquitoes transmitting malaria). Breaking any link in this chain is the key to controlling an outbreak. This is achieved through public health measures such as quarantine to isolate the infected, ensuring safe drinking water, proper sewage disposal, and maintaining high standards of personal and community hygiene to prevent the pathogen from finding a new host.
Beyond prevention, the human body has its own sophisticated defense network known as the immune system. This system provides immunity, which is the body’s ability to resist and fight off infections. Immunity can be innate, which are the general barriers we are born with like skin and stomach acid, or acquired, which is developed over time. A crucial method for acquiring immunity is through vaccination, where a weakened or dead pathogen is introduced into the body. This safely stimulates the immune system to produce antibodies, creating a “memory” that allows for a rapid and powerful response if the real pathogen is encountered in the future, thereby providing long-term protection against specific diseases.
Multiple choice type
Question 1.
A disease widely spread worldwide is known as
- endemic
- epidemic
- pandemic
- Sporadic
Question 2.
The letter B in the name BCG vaccination stands for
- Brief
- Beri-beri
- Bacteria
- Bacillus
Question 3.
Use of disposable syringes for injecting medicines, etc. is specially advised to prevent
- Poliomyelitis
- Mumps
- Rabies
- AIDS
Question 4.
The vector that transmits the malarial pathogen is:
- Culex mosquito
- Housefly
- Anopheles mosquito
- Entamoeba
Question 5.
Amoebiasis is caused by the protozoan:
- Amoeba proteus
- Euglena
- Plasmodium
- Entamoeba
Question 6.
BCG vaccine provides immunity against ______.
- Tetanus
- Cholera
- AIDS
- Tuberculosis
Question 7.
The expanded form of AIDS is
- Active Immunity Deficiency Syndrome
- Acquired Immuno Deficiency Syndrome
- Acquired Immuno Deficiency Status
- Active Immuno Deficiency Syndrome
Very short answer type
Question 1.
1. Mention whether the following statement is true (T) or false (F). Filariasis is transmitted by the housefly.
True
False
2. Mention whether the following statement is true (T) or false (F). Malaria is caused by protozoans.
True
False
3. Mention whether the following statement is true (T) or false (F). BCG vaccine is used for chicken pox.
True
False
4. Mention whether the following statement is true (T) or false (F). Louis Pasteur discovered a cure for malaria.
True
False
5. Which of the following statements is true (T) and which ones are false (F)? AIDS is caused by a bacterium.
True
False
6. Mention Whether the Following Statement is True (T) Or False (F). HIV is a serious disease, usually fatal.
True
False
7. Mention Whether the Following Statement is True (T) Or False (F). AIDS is not transmitted by contact with a patient’s clothes.
True
False
8. Mention whether the following statement is true (T) or false (F). Chicken pox and hepatitis are bacterial diseases.
True
False
9. Mention whether the following statement is true (T) or false (F). Goitre is endemic in sub-Himalayan regions of India.
True
False
10. Mention whether the following statement is true (T) or false (F). AIDS is caused by a fungus.
True
False
11. Mention whether the following statement is true (T) or false (F). Hay fever and asthma are allergies.
True
False
12. Mention whether the following statement is true (T) or false (F). Smallpox still occurs in India.
True
False
13. Mention whether the following statement is true (T) or false (F). The disease filariasis is caused by the bite of the female anopheles mosquito.
True
False
Ans:
Here are the evaluations for each statement:
- Filariasis is transmitted by the housefly. False (Filariasis is transmitted by mosquitoes, primarily the Culex mosquito.)
- Malaria is caused by protozoans. True (It is caused by the Plasmodium protozoan parasite.)
- BCG vaccine is used for chicken pox. False (BCG vaccine is used against Tuberculosis (TB). The Varicella vaccine is used for chicken pox.)
- Louis Pasteur discovered a cure for malaria. False (Louis Pasteur is known for discoveries in vaccination, microbial fermentation, and pasteurization. The cause and treatment of malaria were discovered by others.)
- AIDS is caused by a bacterium. False (AIDS is caused by the Human Immunodeficiency Virus (HIV), which is a virus, not a bacterium.)
- HIV is a serious disease, usually fatal. True (Untreated HIV infection eventually leads to AIDS, which severely compromises the immune system and is considered usually fatal due to opportunistic infections.)
- AIDS is not transmitted by contact with a patient’s clothes. True (HIV is primarily transmitted through specific body fluids: blood, semen, pre-seminal fluid, rectal fluids, vaginal fluids, and breast milk, not through casual contact like clothing.)
- Chicken pox and hepatitis are bacterial diseases. False (Both Chickenpox and Hepatitis (A, B, C, D, E) are caused by viruses, not bacteria.)
- Goitre is endemic in sub-Himalayan regions of India. True (Goitre, caused by iodine deficiency, is historically prevalent in mountainous, sub-Himalayan regions where iodine is naturally depleted from the soil.)
- AIDS is caused by a fungus. False (AIDS is caused by the Human Immunodeficiency Virus (HIV).)
- Hay fever and asthma are allergies. True (Hay fever and asthma attacks are often triggered by an overreaction of the immune system to environmental substances (allergens).)
- Smallpox still occurs in India. False (Smallpox was globally eradicated in 1980 and is no longer found anywhere in the world, including India.)
- The disease filariasis is caused by the bite of the female Anopheles mosquito. False (The female Anopheles mosquito transmits Malaria. Filariasis is primarily transmitted by the Culex mosquito.)
Question 2.
Write the full form of the following as it occurs in biology: AIDS
Ans:
The full form of AIDS as it occurs in biology and medicine is: Acquired Immuno Deficiency Syndrome
Question 3.
1.Name the Following: Category of pathogen that causes diseases like common cold and mumps.
2. Name the following: The vaccine for preventing tuberculosis.
3. Name the following: An organ usually affected by tuberculosis.
4. Name the following: A disease that weakens the body’s defence system against infections.
5. Name the following: Germ of germ-substance introduced into the body to prevent occurrence of an infectious disease.
6. Name the following: The vector responsible for transmission of sleeping sickness.
7. Name the following: The microorganism that requires a host to reproduce.
8. Name the following: The popular name of the disease is filariasis.
Ans:
| Description | Term/Name |
| Category of pathogen responsible for ailments such as the common cold and mumps. | Virus |
| The immunization agent administered to prevent the development of tuberculosis. | BCG vaccine (Bacille Calmette-Guérin) |
| The organ most frequently targeted and damaged by the Mycobacterium tuberculosis infection. | Lungs |
| A pathological condition that compromises the body’s immune system, making the individual susceptible to opportunistic infections. | AIDS (Acquired Immuno Deficiency Syndrome) |
| A biological preparation (live, weakened, or dead microbes/substance) introduced to stimulate immunity against a specific contagious illness. | Vaccine |
| The blood-feeding insect that acts as the carrier for the parasite causing African trypanosomiasis (sleeping sickness). | Tsetse fly (Glossina species) |
| A microbe characterized by its absolute requirement of a living host cell’s machinery to replicate and multiply. | Virus |
| The widely known term for the disease filariasis, characterized by extreme swelling of limbs and body parts. | Elephantiasis |
Short answer type
Question 1.
1.Define the following: Infection
2. Define the following: Pathogen
3. Define the following: Incubation period
4. Define the following: Allergen
Ans:
Here are the definitions for the biological and medical terms requested:
1. Infection
Infection is the invasion and multiplication of pathogenic microorganisms (such as bacteria, viruses, fungi, or parasites) within the body tissues of a host organism. This invasion may lead to tissue damage and elicit an immune response, resulting in disease.
2. Pathogen
A pathogen is any organism or agent (typically a microorganism) that is capable of producing disease in a host. Pathogens include infectious agents such as viruses, bacteria, protozoa, fungi, and worms (helminths).
3. Incubation Period
The incubation period is the time elapsed between the moment a host is exposed to a pathogen (gets infected) and the first appearance of recognizable signs or symptoms of the disease. During this time, the pathogen is typically replicating within the host’s body.
4. Allergen
An allergen is a normally harmless substance (usually a protein) that causes an abnormal, exaggerated, or hypersensitive immune response (an allergy) in susceptible individuals. Common allergens include pollen, dust mite feces, certain foods, and animal dander.
Question 2.
What are the different ways in which infectious diseases can spread?
Ans:
Infectious diseases spread through various methods, which can be categorized based on how the pathogen (the disease-causing agent) moves from a source to a new host.
Modes of Infectious Disease Transmission
1. Direct Contact
This involves the immediate physical transfer of the pathogen from an infected person or animal to a susceptible person.
- Person-to-Person Contact: Includes touching, kissing, sexual contact, or contact with oral secretions or body lesions (e.g., common cold, AIDS, mononucleosis).
- Droplet Spread: Pathogens are contained in droplets of mucus or saliva expelled during coughing, sneezing, or talking. These large droplets only travel short distances (usually less than one meter) before settling (e.g., influenza, some bacterial infections).
2. Indirect Contact
This involves an intermediate step between the source and the host.
- Fomites (Contaminated Objects): The pathogen is transferred via an inanimate object (a fomite) that an infected person has touched. This includes doorknobs, shared utensils, towels, or contaminated syringes (e.g., staph infections, gastroenteritis).
- Airborne Transmission: Pathogens remain suspended in the air over long distances (greater than one meter) after a person coughs or sneezes. These tiny particles can be inhaled by others (e.g., tuberculosis, measles).
3. Vehicle Transmission
This occurs when a single, contaminated source transmits the infection to multiple people simultaneously.
- Waterborne: Contaminated public or untreated water supplies act as a vehicle (e.g., cholera, Hepatitis A).
- Foodborne: Improperly handled, stored, or cooked food transmits the infection (e.g., Salmonella or E. coli).
- Blood/Body Fluids: Pathogens transmitted through contaminated blood products, medical devices, or shared needles (e.g., Hepatitis B, HIV).
4. Vector Transmission
This involves living organisms (vectors) that carry the pathogen from one host to another.
- Mechanical Vectors: The vector (like a housefly) passively carries the pathogen on its body parts (legs, mouth, etc.) from feces or filth to food (e.g., dysentery).
- Biological Vectors: The vector (like a mosquito or tick) hosts the pathogen, often undergoing a part of its life cycle inside the vector, and then transmits it through a bite (e.g., malaria transmitted by Anopheles mosquitoes, Lyme disease transmitted by ticks).
Question 3.
Name any four non-infectious diseases and their causes.
Ans:
| Disease | Primary Cause(s) |
| 1. Type 2 Diabetes Mellitus | A combination of lifestyle factors (unhealthy diet high in sugar and calories, physical inactivity) leading to obesity and subsequent insulin resistance, where the body’s cells do not respond effectively to insulin. Genetics also play a role. |
| 2. Cardiovascular Disease (CVD) | Primarily caused by atherosclerosis (the build-up of fatty plaques inside arteries), which is largely driven by modifiable risk factors like smoking, high blood pressure (hypertension), high cholesterol, unhealthy diet, and lack of exercise. |
| 3. Cancer | The uncontrolled growth and division of abnormal cells resulting from damage or mutation to DNA. Causes include exposure to carcinogens (e.g., tobacco smoke, UV radiation), genetic predisposition, and certain chronic infections (though the disease itself is non-infectious). |
| 4. Asthma | Chronic inflammation and narrowing of the airways, often triggered by a hypersensitivity (allergy) to substances like pollen, dust mites, or pet dander. Other causes include genetic predisposition and environmental factors (e.g., air pollution). |
Question 4.
Why is it important to know how the germs leave the body of a patient?
Ans:
It is crucial to know how germs leave the body of a patient because this information directly identifies the pathways of transmission, which is essential for breaking the chain of infection and preventing the disease from spreading to other people.
Reasons for Knowing Exit Routes
- Implementing Isolation and Containment: Knowing the exit route allows medical professionals to implement the correct isolation procedures. For example:
- If a germ leaves via respiratory droplets (e.g., coughing, sneezing), the patient needs a private room and others must wear masks.
- If a germ leaves via feces (e.g., cholera), strict handwashing, proper sanitation, and safe disposal of waste are mandatory.
- Developing Preventive Measures: Understanding how the pathogen exits determines the necessary public health interventions.
- For germs leaving through the skin (e.g., scabies), avoiding direct contact is key.
- For germs leaving through blood (e.g., HIV), safe needle practices and blood screening are required.
- Targeting Vectors and Vehicles: The exit route often points to the next step in the spread. If a germ leaves through open sores or blood, it might be picked up by a vector (like a mosquito or fly), which must then be controlled.
- Effective Treatment and Hygiene: It informs healthcare workers and caregivers about where the highest concentration of the pathogen exists, guiding them on the specific hygiene and disinfection protocols needed to protect themselves and the environment.
Question 5.
Name the causative germ of AIDS. How is this disease transmitted?
Ans:
The causative germ of AIDS (Acquired Immunodeficiency Syndrome) is the Human Immunodeficiency Virus (HIV).
Transmission of HIV
HIV is transmitted through the exchange of specific body fluids from an infected person to a non-infected person. Transmission requires contact with blood, semen, pre-seminal fluid, rectal fluids, vaginal fluids, or breast milk.
The most common ways the disease is transmitted are:
- Unprotected Sexual Contact: Through vaginal, anal, or oral sex without the use of barrier methods (like condoms).
- Sharing of Contaminated Needles: This occurs primarily among intravenous drug users who share needles, syringes, or other drug injection equipment.
- Mother-to-Child Transmission (MTCT): The virus can be passed from an infected mother to her child during pregnancy, childbirth, or breastfeeding.
- Blood Transfusions and Products: While extremely rare today due to rigorous screening of blood donations, transmission can occur through transfusions of unscreened blood.
Long answer type
Question 1.
1.Write very briefly about the following: BCG
2. Write very briefly about the following : Incubation period
3. Write very briefly about the following: Chicken pox
4. Write very briefly about the following: Hepatitis A
Ans:
Here are brief summaries of the requested terms:
1. BCG
BCG stands for Bacille Calmette-Guérin. It is a vaccine primarily used against Tuberculosis (TB), a serious bacterial infection. It is a live, attenuated (weakened) vaccine that helps stimulate the immune system to recognize and fight the Mycobacterium tuberculosis bacterium.
2. Incubation Period
The incubation period is the time interval between the moment a susceptible person is infected with a pathogen (the time of exposure) and the appearance of the very first signs or symptoms of the disease. This duration varies greatly depending on the specific disease (e.g., hours for influenza, weeks for measles, years for HIV).
3. Chickenpox (Varicella)
Chickenpox is a highly contagious viral infection characterized by an itchy, blister-like rash all over the body. It is most common in children and spreads easily through airborne transmission and direct contact. Once contracted, it typically confers lifetime immunity.
4. Hepatitis A
Hepatitis A is a viral liver disease caused by the Hepatitis A virus (HAV). It is primarily transmitted via the fecal-oral route, typically through the ingestion of contaminated food or water, or through direct contact with an infected person. It causes symptoms like fever, fatigue, and jaundice, but it is an acute infection that usually resolves on its own and does not lead to chronic liver disease.
Question 2.
What are the causes and symptoms of malaria, chicken pox and tuberculosis? How can these diseases be prevented?
Ans:
1. Malaria
| Aspect | Description |
| Cause | A protozoan parasite of the genus Plasmodium (most commonly P. falciparum). |
| Transmission | Transmitted to humans through the bite of an infected female Anopheles mosquito (the vector). |
| Symptoms | Recurrent attacks of high fever accompanied by severe shaking chills and profuse sweating. Other symptoms include headache, nausea, and vomiting. |
| Prevention | Mosquito control (eliminating standing water, using larvicides), use of mosquito nets (especially insecticide-treated nets), wearing long sleeves and pants, and taking prophylactic (preventive) anti-malarial drugs in endemic areas. |
2. Chickenpox (Varicella)
| Aspect | Description |
| Cause | The Varicella-Zoster Virus (VZV), a type of herpes virus. |
| Transmission | Highly contagious; spread through airborne droplets from coughing or sneezing, or by direct contact with fluid from the blisters. |
| Symptoms | A characteristic itchy rash that develops into fluid-filled blisters (vesicles) that eventually crust over. Usually accompanied by fever, headache, and general feeling of illness (malaise). |
| Prevention | Vaccination (Varicella vaccine) is the most effective method. Avoiding close contact with infected individuals and practicing good respiratory hygiene also help. |
3. Tuberculosis (TB)
| Aspect | Description |
| Cause | A bacterium called Mycobacterium tuberculosis. |
| Transmission | Spread through the air when a person with active pulmonary TB coughs, sneezes, or talks, releasing aerosolized droplets containing the bacteria. |
| Symptoms | Persistent, severe cough often lasting three weeks or longer, sometimes producing blood-tinged sputum. Other symptoms include chest pain, unintentional weight loss, fever, and night sweats. |
| Prevention | The BCG vaccine is given to infants in many countries to protect against severe forms of TB. Practicing good cough etiquette (covering the mouth and nose) and, for exposed individuals, taking preventive drug therapy (isoniazid) are key. |
