Among many epidemiologic triad or triangle, the traditional model for an infectious disease (The triad ) consists of an external agent, a susceptible host, and an environment. So, the correct option B ( Host, agent, and environment )

Neutrophils. The first immune cells that arrive at an injured site are mostly neutrophils, which are quick-response immune cells that recognize and destroy bacteria. 

Infectious diseases are those diseases which are caused by microorganisms like fungi, bacteria, virus, parasites. HIV (Human immunodeficiency virus) causes AIDS (Acquired immunodeficiency syndrome). It is a sexually transmitted disease. Diphtheria is caused by bacterium Corynebacterium diphtheria. It affects the mucous membrane of throat and upper respiratory tract. Coronary thrombosis is a disease that results due to accumulation of blood clot on the walls of arteries. Diabetes mellitus is a disease that results due to insufficient production of insulin in the body.

The limitations that are confronted while treating an infectious disease are that the impaired body functions happened due to the infection cannot recover completely, the patient is asked to have complete bed rest and infectious disease can spread from one person to another as it a contentious disease.

Pellagra or red sickness is a vitamin deficiency disease caused by chronic lack of Vitamin B3 in the diet. It can also be caused by the decreased intake of niacin or tryptophan. Described as three D's diarrhea, dermatitis, and dementia, this is indicated by symptoms such as dermatitis, alopecia or hair loss, edema or swelling, red skin lesions, weakness and mental confusion.

Mosquito-borne diseases or mosquito-borne illness are disease caused by bacterial, viruses or parasites transmitted by mosquitoes. They can transmit disease without being affected themselves. Mosquito vectored diseases include protozoan diseases, i.e., malaria, filarial diseases, and viruses such as dengue, encephalitis and yellow fever. 

• Measles, mumps, rubella, and varicella (commonly known as chickenpox), influenza are the chronic diseases of a virus. 
• These can be prevented from spreading by using vaccines. This vaccine works by prior exposure of a small dose of the virus or a protein from the virus, which activates the immune response.

Some infectious diseases can be passed from person to person. Some are transmitted by bites from insects or animals. And others are acquired by ingesting contaminated food or water or being exposed to organisms in the environment. Therefore, (d) is the correct answer.

Vector borne diseases are illnesses caused by an infectious microbe that is transmitted to vertebrates by another animal, usually an arthropod. This second animal is called a vector for the disease. There are a large number of viral, bacterial and parasitic diseases that can be transmitted by insect vectors. The most common vectors are blood sucking insects such as mosquitoes, fleas, lice, biting flies, bugs, lice, helminths and ticks. Most common vector borne diseases affecting people and their vectors are: malaria -anopheles mosquitoes, dengue and chikungunya - aedes mosquitoes, Leishmaniasis (kala azar) - sandflies, trypanosomiasis (gambia fever) - flies and bugs, filariasis - mosquitoes, encephalitis - mosquitoes and ticks, yellow fever - mosquito, plague - flies, lyme disease - ticks etc.

Pathogen is an infectious agent such as a virus, bacterium, prion, fungus, viriod or parasite that causes disease in its host. The host may be an animal, a plant, a fungus, or even another microorganism.

Food prepared in unhygienic conditions can lead to diseases. Use of contaminated water, dirty utensils, not washing raw materials before cooking, inappropriate cooking practices are all source of contamination and can result in infection. Therefore, (a) is the correct answer.

Pathogen is the term used to describe an infectious agent that causes disease in the host. Therefore, (a) is the correct answer.

Air, water and soil are carriers of infectious organisms. Soil can cause contamination of plants and infect them and hence, the human. Air is the most common carriers of pathogens around us. Therefore, (d) is the correct answer.

There are numerous ways through which infections can be transmitted. Coughing by the infected person can cause transfer as the organisms coming out are inhaled by the healthy person. No use of proper sanitization can also cause transmission of diseases. Therefore, (b) is the correct answer.

Latent infection is one which do not show any signs or symptoms at first but can naturally develop over time. Therefore, (a) is the correct answer.

Measles is caused by the type of paramyxovirus known as rubella virus.

Explanation: It is an actual infectious disease of cattle, buffalo, sheep and goat. It distances transportation. In India, the disease is enzootic in nature. Etiology environmental conditions, malnutrition and long distance transportation. In India, the disease is enzootic in nature.

Encephalitis is the disorder in which there is inflammation of the meninges of the brain. This disease may be caused due to bacterial or viral infection and is transmitted by the vector which is the Culex mosquito. Malaria is a disorder which is caused by the protozoan Plasmodium vivax. The disease is transmitted by the Anopheles mosquito. 

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• A disease vector is an agent who carries and transmits an infectious pathogen into another living organism.
• Female Anopheles mosquito serves as vector for malaria.
• Musa(house fly)serves as a vector for at least 65 diseases to humans, including typhoid fever, dysentery, cholera, poliomyelitis, yaws, anthrax, tularemia, leprosy, and tuberculosis.
• Culex mosquito serves as a vector for arbovirus infections such as West Nile virus, Japanese encephalitis, or St. Louis encephalitis, but also filariasis.
• Hence Vectors are Anopheles, Musca, and Culex.
• So, the correct answer is 'Anopheles, Musca, and Culex'.

Droplet infection is an infection transmitted from one individual to another by droplets of moisture expelled from the upper respiratory tract through sneezing or coughing. Direct transmission occurs when there is physical contact between an infected person and a susceptible person. Droplet infection is a mode of direct transmission in which the infection is transmitted by coughing, sneezing.

• Diseases transmitted by mosquitoes include: malaria, dengue,Yellow fever,Elephantiasis West Nile virus, chikungunya, filariasis, tularemia, dirofilariasis, Japanese encephalitis, Saint Louis encephalitis, Western equine encephalitis, Eastern equine encephalitis, Venezuelan equine encephalitis, Ross River fever, Barmah Forest fever, La Crosse encephalitis, and Zika fever,as well as newly detected Keystone virus and Rift Valley fever.
• Out of pneumonia, gangrene, yellow fever, dengue fever, malaria and elephantiasis, mosquitoes transmit 4 diseases they are Yellow fever, dengue, malaria, and elephantiasis.
  
• So, the correct answer is '4'.

• A disease vector is an agent who carries and transmits an infectious pathogen into another living organism.
• Vector-borne diseases are human illnesses caused by parasites, viruses, and bacteria that are spread by insects like mosquitoes, sandflies, triatomine bugs, black flies, ticks, tsetse flies, mites, snails and lice. For example, Female Anopheles mosquito is a vector for malaria.
• Hence Vector insects are which spread disease.
  
• So, the correct answer is 'Spread disease'.

• African trypanosomiasis, also known as sleeping sickness, is an insect-borne parasitic disease of humans and other animals. It is caused by protozoa of the species Trypanosoma brucei. It is transmitted by the bite of an infected tsetse fly which acts as a vector.
  
• Malaria is a mosquito-borne infectious disease affecting humans and other animals caused by Plasmodium species. The disease is most commonly transmitted by an infected female Anopheles mosquito which acts as a vector.
  
• Kala-azar is a disease caused by protozoan parasites belonging to genus Leishmania. The disease is transmitted by insects which act as vectors such as sand fly.

Biological agents which cause disease are known as pathogens that are the micro-organisms which when successfully infect the human body, multiply and produce toxins in incubation period which interfere with the normal functioning of the body and cause disease. A virus is a small, infectious, biological agent that replicates only inside the living cells of other organisms.

• Malaria is caused by a one-celled parasite called a Plasmodium. Female Anopheles mosquitoes pick up the parasite from infected people when they bite to obtain blood needed to nurture their eggs. Inside the mosquito, the parasites reproduce and develop.
• In Filariasis, mosquitoes can transmit the parasite, depending on the geographic area. In Africa, the most common vector is Anopheles. During a meal, an infected mosquito introduces third-stage filarial larvae onto the skin of the human host, where they penetrate into the wound. 
• Hence, Plasmodium ovale and Wuchereria bancrofti human parasites require mosquito to complete their life cycle.
• So, the correct answer is 'Plasmodium ovale and Wuchereria bancrofti'

A fomite is any nonliving object or substance capable of carrying infectious organisms, such as viruses or bacteria, and hence transferring them from one individual to another. Fomites are associated particularly with hospital-acquired infections, as they are possible routes to pass pathogens between patients. Researchers have discovered that smooth (non-porous) surfaces like doorknobs transmit bacteria and viruses better than porous materials like paper money.

Pneumonia is an inflammatory condition of the lung affecting primarily the small air sacs known as alveoli. Symptoms include some combination of a productive or a dry cough, chest pain, fever, and trouble breathing. Pneumonia may spread via airborne droplets from a cough or sneeze. Pneumonia is usually caused by infection with viruses or bacteria and less commonly by other microorganisms, certain medications and conditions such as autoimmune diseases.

• Measles is a highly contagious infectious disease caused by the measles virus. Symptoms include fever, often greater than 40 °C, cough, runny nose, and inflamed eyes. Measles is an airborne disease which spreads easily through the coughs and sneezes of infected people.
  
• Diphtheria is an infection caused by the bacterium Corynebacterium diphtheriae. Symptoms include a sore throat and fever. In severe cases, a grey or white patch develops in the throat. Diphtheria is usually spread between people by direct contact or through the air (droplet).
  
• Pertussis, commonly known as a Whooping cough is a highly contagious bacterial disease. Symptoms include a runny nose, fever, and cough. Pertussis is caused by the bacterium Bordetella pertussis. It is an airborne disease which spreads easily through the coughs and sneezes of an infected person.
• Gonorrhoea is a sexually transmitted infection caused by the bacterium Neisseria gonorrhoeae. Symptoms include burning with urination, discharge from the penis, or testicular pain. Women may have burning with urination, vaginal discharge, vaginal bleeding between periods, or pelvic pain. Hence, it is not transmitted by droplets.

• Droplet infection is an infection transmitted from one individual to another by droplets of moisture expelled from the upper respiratory tract through sneezing or coughing.
• Pneumonia is an inflammation of the parenchyma of the lungs. It is caused by the bacterium Streptococcus pneumoniae.
• Symptoms include a cough with phlegm or pus, fever, chills and difficulty breathing.
• The bacteria that are commonly found in the nose or throat, can infect the lungs if they are inhaled. They may also spread via airborne droplets from a cough or sneeze.
• So, the correct answer is '.Pneumonia ,Streptococcus pnemoniae,Droplet infection'.

Vectors are the organisms, which carries the infectious agents from sick person to another healthy person. For example, mosquito carries malarial parasite from infected person to healthy person. Therefore, option A is correct.

Wuchereria bancrofti is a human parasitic roundworm that is the major cause of lymphatic filariasis. W. bancrofti carries out its lifecycle in two hosts. Humans serve as the definitive host and mosquitos as the intermediate host or vector. The microfilariae are transferred into a vector i.e., female Culex mosquito. Hence, female Culex act as a vector of Wuchereria bancrofti.

• Meningitis is the Inflammation of the brain and spinal cord membranes, typically caused by an infection.
• If the meningitis is caused by bacterium Neisseria meningitidis, it is called as Meningococcal meningitis.
• Symptoms include pain in sudden high fever, severe persistent headache, neck stiffness, nausea or vomiting, joint pains, drowsiness, confusion, etc.
• People spread meningococcal bacteria to other people by sharing respiratory and throat secretions (saliva or spit) when they cough or sneezes.
  
• Hence Meningococcal meningitis infection is transmitted chiefly from person to person.
• So, the correct answer is 'Meningococcal meningitis.

When children play barefoot in pools of dirty water and flood water, they may suffer from Leptospirosis and bilharzia. 

Disease causing microbes can spread through the air. This occurs through the little droplets thrown out by an infected person who sheezes or coughs. Another person standing close by can breathe in these droplets and the microbes infect him also. Diseases which spread like this are common cold, pneumonia and tuberculosis.

So, the correct answer is 'Option 'First line defence - Fever' and 'Third line defence - AMI'.'

Amniocentesis is used to detect hereditary and enzymatic abnormalities in the foetus. Down's syndrome cystic fibrosis and colourblindness are genetic disorders while jaundice is an infectious disease.

• House flies are not the neatest of insects. They visit such places as dumps, sewers, and garbage heaps. They feed on faecal matter, discharges from wounds and sores, sputum, and all sorts of moist decaying matter such as spoiled fish, eggs and meat. House flies are strongly suspected of transmitting at least 65 diseases to humans, including typhoid fever, dysentery, cholera, gangrene, poliomyelitis, yaws, anthrax, tularemia, leprosy and tuberculosis. Flies regurgitate and excrete wherever they come to rest and thereby mechanically transmit disease organisms.
• Pertussis, also known as whooping cough, is a highly contagious respiratory disease. It is caused by the bacterium Bordetella pertussis. Pertussis is known for uncontrollable, violent coughing which often makes it hard to breathe.
• Pertussis, also known as whooping cough, is a highly contagious respiratory disease. It is caused by the bacterium Bordetella pertussis. Pertussis is known for uncontrollable, violent coughing which often makes it hard to breathe.

The common cold is an infectious disease caused by rhinovirus. It causes inflammation of upper respiratory tract.

• Wuchereria bancrofti is commonly called the Filarial worm as it causes Filariasis or Elephantiasis in humans. It lives in the lymph vessels of man and female Culex mosquito is its secondary host and acts as a vector. Yellow fever (YF) is an African mosquito-borne infection of primates. It is caused by a virus of the Flavivirus genus of the Flaviviridae family. In its natural habitat, it is transmitted between monkeys by forest-dwelling primatophilic Aedes mosquitoes.
• Aedes mosquitoes cause yellow fever and filarial worm cause Filariasis. 
•  Malaria, caused by Female Anopheles mosquitoes pick up the parasites by feeding on infected humans. The parasites develop in a mosquito’s body for 10 to 18 days, then is passed on when the mosquito injects saliva while feeding.
• The Oriental Rat flea (Xenopsylla cheopis), also known as the tropical rat flea, is a parasite of rodents, primarily of the genus Rattus, and is a primary vector for bubonic plague and murine typhus. This occurs when the flea has fed on an infected rodent, and then bites a human. Diarrhoea is when your bowel movements become loose or watery. The definition of diarrhoea is passing loose or watery bowel movements 3 or more times in a day (or more frequently than usual). Diarrhoea occurs when the lining of the intestine is unable to absorb fluid, or it actively secretes fluid. 
• .

An airborne disease is any disease that is caused by pathogens and transmitted through the air. all respiratory droplets. The airborne transmission that occurs utilizes small particles or droplet nuclei that contains these infectious agents or pathogens. These particles and droplets are capable of remaining suspended in air for extended periods of time. Inhalation of these particles results in respiratory tract infection. Whooping cough (Bordetella pertussis), meningitis (Neisseria species), diphtheria (Corynebacterium diphtheriae), pneumonia (Mycoplasma pneumoniae, Streptococcus species) and tuberculosis (Mycobacterium tuberculosis) are some of the bacterial diseases that spread through air. 

Cholera is caused by a bacterium called Vibrio cholerae. A person gets cholera by drinking water or eating food infected with the bacterium. Once swallowed, it settles in the lining of the small bowel and releases a toxin (poison) that can cause the body to flush liquid into the small bowel, resulting in watery diarrhoea. Typhoid fever is an acute illness associated with fever caused by the Salmonella typhi bacteria. The bacteria spread through contaminated food or water and occasionally through direct contact with someone who is infected. 

City dwellers are facing the acute problems of water and vector borne diseases due to water logging and improper solid waste management and sanitation. The water logging and reprehensible drainage, contamination of water of upper layer from which major portion of the people get the polluted water through shallow bored hand pumps for drinking and other domestic purposes, are main cause of water borne diseases in the city. It is evident from studies that about 70.5 % population is suffering from the abdomen diseases cause by using polluted and contaminated water. Japanese encephalitis, jaundice, cholera, colitis, diarrhoea, dysentery, typhoid and skin diseases are common.

Cobras belong to the elapids sub-group of snakes and there

are over 270 species of cobras. Cobra's venom

contains postsynaptic neurotoxins that spread rapidly into the victim's

bloodstream and affects the lungs causing respiratory failure and eventually, death.

The diseases which are transmitted through contaminated air are known as airborne diseases. When the person lives in an overcrowded area which is poorly ventilated house, the person may suffer from breathing and airborne related diseases. The person may suffer from respiratory infections and disorders.

The disease can be transmitted directly or indirectly depending on the surrounding factors like example air , water and soil. Therefore, (b) is the correct answer.

Insects like mosquitoes act as a vector to transfer infection from one host to another. This happens when one mosquito sucks blood from the infected person and the same mosquito bites a healthy person.  Therefore, (a) is the correct answer.

Direct transmission is communicable and contagious disease. It is spread from one infected person to the host. It can be transferred due to direct sexual contact, through air in the form of sneezing or coughing, through contaminated food and water due fecal matter etc. Therefore, (d) is the correct answer.

Fomites are surfaces which are frequently touched and hence infected. There can be many items used by the infected person like door knobs, handles, computer keyboards, pen, toys phone etc. Therefore, (d) is the correct answer.

Infections can also be transmitted through contaminated air, soil, water, surroundings etc. Food not prepared in hygienic conditions can also cause infection. Therefore, (c) is the correct answer.

Indirect Transmission is the spread of disease from host to host by means of a vector. Therefore, (b) is the correct answer.

Becoming exposed to or infected with an infectious microbe does not necessarily mean developing disease. This can be an advantage to people with good immune system. Proper nourishment and food will give rise to a healthy immune system. Therefore, (a) is the correct answer.

Particles containing organisms which can remain in air for long time Solution:- Dust particles containing microorganisms which can remain in air for longer duration of time results in airborne transmission. They must be resistant to drying and can survive for long outside the body. Therefore, (b) is the correct answer.

Explanation: It is an acute infectious and highly fatal, bacterial disease of cattle. Buffaloes, sheep and goats are also affected. Young cattle between 6-24 months of age, in good body condition are mostly affected. It is soil-borne infection which generally occurs during rainy season. In India, the disease is sporadic (1-2 animal) in nature. It is caused by Clostridium chauvoei.

The mosquitoes act as a vector and help in the transmission of several diseases. Dengue fever is transmitted by the biting of the Aedes mosquito and the malaria is transmitted by the biting of the female Anopheles mosquito. 

An allergen is a type of antigen which are non-infectious that produces an abnormally vigorous immune response in which the immune system fights off a perceived threat that would otherwise be harmless to the body. Such reactions are called allergies. The production of allergens stimulates the release of IgE (immunoglobulin E) antibodies. These IgE antibodies bind to the allergens and then activates receptors of mast cells which triggers the release of inflammatory chemicals such as histamine. Hence, allergens induce disorders through secretion of IgE and histamine.

• Dracunculus medinensis or Guinea worm is a nematode that causes dracunculiasis( guinea worm disease).
  
• Usually, the disease has no initial symptoms. About one year later, there is a painful burning feeling as a blister forms, usually on the legs. The blister bursts as the worm then come out of the skin over a few weeks.
• this Disease has been eradicated and India was declared as guinea worm disease free country by WHO in 2000.
• Hence The parasite which has been recently eradicated from India is Dracunculus medinensis.
• So, the correct answer is 'Dracunculus medinensis '.

Many microbial agents can commonly move from an affected person to someone else in a variety of ways. Such disease-causing microbes can spread through the air. This occurs through the little droplets thrown out by an infected person who sneezes or coughs. Someone standing close by can breathe in these droplets, and the microbes get a chance to start a new infection. Examples of such diseases spread through the air are the common cold, pneumonia and tuberculosis. Obviously, the more crowded our living conditions are, the more likely it is that such airborne diseases will spread.

Brain fever is caused by virus and transmitted through Culex tritaeniorhynchus, female mosquitoes. Mosquitoes acquire virus, while taking blood meal and pass it to next healthy person. 
When Anopheles female mosquito bites a malaria patient then malarial parasite also enters in mosquito, while blood suction. Malarial parasite can grow in mosquito body and pass to another person, when mosquito bites. Dengue virus is transmitted due to mosquitoes, Aedes aegypti.  
Typhoid is caused by bacteria called as Salmonella typhi. It is water borne disease. Typhoid patient's feces show presence of Salmonella typhi. When such feces comes in contact with drinking water bodies then water gets polluted. Such, water if used for consumption then person gets infected with typhoid. Hence, typhoid is not transmitted by mosquito. 

Foodborne illness can be caused by pesticides or medicines in food and naturally toxic substances such as poisonous mushrooms or reef fish. Foodborne illnesses may result from the consumption of food contaminated by microbial pathogens, toxic chemicals or radioactive materials. The temperature range in which food-borne bacteria can grow is known as the danger zone. Food safety agencies, such as the United States' Food Safety and Inspection Service (FSIS), define the danger zone as roughly 4–5°C to 60 °C. The FSIS stipulates that potentially hazardous food should not be stored at temperatures in this range in order to prevent foodborne illness. The delay between consumption of a contaminated food and appearance of the first symptoms of illness is called the incubation period. This ranges from hours to days, depending on the agent, and on how much was consumed. 

Contamination of drinking water sources by sewage can occur from raw sewage overflow, septic tanks, leaking sewer lines, land application of sludge and partially treated waste water. Sewage is a complex mixture and can contain many types of contaminants. The greatest threats posed to water resources arise from contamination by bacteria, nitrates, metals, trace quantities of toxic materials, and salts. Seepage overflow into drinking water sources can cause disease from the ingestion of microorganisms such as E coli, Giardia, Cryptosporidium, Hepatitis A, and helminths. Septic tanks are enclosures that store and process wastes by bacterial decomposition. Badly constructed percolation systems may allow water to escape without proper treatment.This water may seep to the land surface, runoff into surface water or flow directly into the water table causing waterborne diseases like cholera, typhoid, diarrhoea etc.

Airborne diseases are caused by pathogenic microbes small enough to be discharged from an infected person via coughing, sneezing, laughing and close personal contact or aerosolization of the microbe. The discharged microbes remain suspended in the air on dust particles, respiratory and water droplets. Illness is caused when the microbe is inhaled or contacts mucus membranes or when secretions remaining on a surface are touched. Many common infections can spread by airborne transmission at least in some cases, including: anthrax (inhalational), chicken pox, influenza, measles, smallpox, and tuberculosis.

An airborne disease is any disease that is caused by pathogens and transmitted through the air. Potato virus is transmitted by aphids by sticking to aphid mouth parts (stylet). The virus can be acquired from the infected plant within seconds, and transmitted to a healthy plant very fast. It can also be transmitted mechanically by machinery, tools, and damaging plants while walking through the field. Aphids are by far the most efficient means of transmission.

Salmonella bacteria can be found in food products such as raw poultry, eggs, and beef, and sometimes on unwashed fruit. Food prepared on surfaces that previously were in contact with raw meat or meat products can, in turn, become contaminated with the bacteria. This is called cross-contamination.

Explanation: The most common type of enteritis is caused by food poisoning. You get it after ingesting food or water that is contaminated with bacteria.

Housefly transmits various diseases like typhoid diarrhoea, dysentery, cholera, tuberculosis etc.

Chronic diseases last for a long time, even as much as a lifetime. The chronic diseases have drastic long term effects on patient's health.

Dialysis is the procedure used for cleaning the blood of a person by reparating the waste substance (urea) from it.

Explanation: Chickenpox causes a rash and can make a child feel generally unwell. Treatment aims to ease symptoms until the illness goes. Full recovery in a week is usual in children.

Hepatitis causes liver failure or liver cancer. Due to this the functioning of liver disturbs drastically. This results in jaundice being one of the symptoms of hepatitis.