Disease-causing organisms, i.e. causative agents are transferred from a diseased person to a healthy person by an organism which itself does not get the disease. Such an agent is called “vector”.

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).

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.

AIDS stands for Acquired Immuno Deficiency Syndrome. It is a disease in which a person’s immune system becomes weak and is unable to fight infections. Hence, the concerned person finally dies due to other infections like common cold, sore throat, flu, etc. At the last stage, the person suffers from physical trauma due to infection and inability to treat it.

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.

Diarrhea is an acute disease as it lasts only for a short period.

Vaccination is given to an individual in order to prevent a disease. Antibiotics and drugs are given to cure the diseases.

Viruses are not affected by antibiotics as they use the biochemical mechanisms of their host.

Anthrax is caused by bacteria.

Malaria is caused by a protozoan Plasmodium, which is transmitted by a vector, i.e. female anopheles mosquito.

Hygienic conditions help to prevent illness in an individual.