Why Do We Fall Ill

Clean boiled water with sugar and salt added to it is given to avoid dehydration of body tissues. Our body loses excess of water during stomach and intestinal infection due to loose stools. This happens during gastrointestinal disorder.
In brain, kidney and liver disorders, our body does not lose excess of water and hence, the above said water + sugar + salt does not need to be administered.

During any accident, wounds occur and they are exposed to air and soil. The air and soil may contain tetanus-causing microbes. Hence, the person is immediately given anti-tetanus injection. 

A person will be healthy if he eats a proper diet (option 3), lives in a hygienic environment (option 4) and keeps his body fit by exercising regularly (option 1). Thus, options (1), (3) and (4) help a person to be healthy as these habits keep the germs away and thus, reduce the chances of getting infected by diseases. But, drinking alcohol is not a healthy practice as it adversely affects the nervous system and its prolonged consumption adversely affects the liver and general body health. Thus, (2) is the correct answer because drinking alcohol is responsible for the ill health of a person.

Most of the skin infections are caused by fungi. For example, ringworms. Bacteria and viruses cause internal infections like TB, influenza, etc. Mosquitoes can cause rashes on skin (it is not a disease) and may also transmit other diseases (not related to skin). Thus, (1), (2) and (3) are not suitable. So, only (4) is correct.

Bacterial diseases are those diseases that are caused and transmitted by different bacteria. Typhoid, cholera and tuberculosis are caused by bacteria namely Salmonella typhii, Vibrio cholera and Bacillus calmettie, respectively. Dengue fever is caused by a virus, which is transmitted by the vector Aedes mosquito. Hence, option (3) is the correct answer.

Trypanosoma is responsible for sleeping sickness.

Pneumonia spreads through air. It is an inflammatory condition of the lung affecting primarily the microscopic air sacs known as alveoli. 

Haemophilia is a disease in which the blood does not clot whenever there is a wound/injury and it is a genetic disorder. It is not caused or spread by infectious agents. Thus, it is a non-infectious disease. Cholera, typhoid and malaria are caused due to microorganisms, which cause infection or disease in the digestive system, immune system and blood (also liver), respectively.

Penicillin blocks the bacterial processes that build the cell wall.

AIDS is a viral disease caused by HIV. The human body cannot develop immunity against it. The antibodies that human immune system makes to fight HIV are not effective. HIV actually targets, invades and then destroys some of the most important cells in the immune system itself. So, no vaccine is effective in preventing AIDS.
 

Anthrax is a bacterial disease and can be cured with antibiotics. All the other are viral diseases and antibiotics are not effective against viral diseases.

Tuberculosis is a chronic disease as it can last for a long time, even as much as a lifetime.

Malaria is caused by a protozoan.

Rabies virus is carried by vectors, which contain the virus and transmit it from a diseased person to a healthy person. The vectors for rabies are animals (dogs and cats usually).

Health is a state of being well enough to function well physically, mentally and socially. An individual can be in poor health without having any identifiable disease.

SARS is a respiratory disease caused by a virus. Symptoms usually occur about 2 to 10 days after coming in contact with the virus.

Edward Jenner created the vaccine for smallpox two centuries ago.

Penicillin is an antibiotic obtained from the fungus ‘Penicillium notatum’ and it works against bacteria. Quinine and chloroquine are drugs that are used to treat malaria. Anti-tetanus serum is a vaccine used to prevent tetanus.

Viruses do not have defined body structures or body physiologies. They use the machinery of host cells and live life on that. Hence, it is difficult to control them because we cannot prepare drugs to arrest any step of their physiology because those drugs will actually affect our own (host) cells and harm us. Hence, it is very difficult to prepare drugs against viruses. On the contrary, the physiologies of bacteria, fungi and protozoa are well known and the reactions are different from host cells. We can easily prepare drugs to attack those specific reactions.

When water sources, including private wells, are contaminated with faeces from infected humans, the water will spread the hepatitis A virus to others who drink this water. The virus can enter water supplies through sewage overflows or from broken sewage systems. This virus cannot travel through air and also does not spread by physical contact. An infected mother also cannot pass it on.

Headache and unconsciousness are ailments related to the nervous system, i.e. they are related to the brain. Also, the brain has a part called medulla, which controls the stimuli for vomiting.

An active immune system recruits many cells to the affected tissue to kill off the disease-causing microbes. This recruitment process is called inflammation.

(a) Acute diseases: These diseases are severe, but short-spanned and get less time to cause prolonged poor health.
(b) Chronic diseases: These diseases last for longer periods of time and take sufficient time to affect different parts of the body and lead to a poor health, which recovers after a long time.
(c) Infectious diseases: These diseases spread from a diseased person to a healthy person due to the transmission of disease-causing organisms (for example, common cold).
(d) Non-infectious diseases: These diseases do not spread from one person to another. For example, heart ailment, cancer, etc. They are not caused by infectious agents. The causative agents of these diseases are internal factors. 

Liver is targeted during jaundice.