Ulcers is a bacterial disease caused by Helicobacter pylori. It is a spiral-shaped bacterium that grows in the digestive tract and has a tendency to attack the stomach lining.

Malaria is caused by various species of plasmodia, usually carried by anopheles mosquito.

A virus is a small infectious agent that replicates only inside the living cells of other organisms. Influenza is a viral infection that affects mainly the nose, throat, bronchi and, occasionally, lungs. Chickenpox is caused by the herpes zoster virus and mainly affects children.

AIDS is caused by a virus known as HIV (human immunodeficiency virus). Rest of them are caused by protozoa.

Human excreta has caused major impact on transferring many diseases to humans including cholera, polio, typhoid and ascariasis.

Kala-azar is leishmaniasis. It is caused by protozoans.

AIDS stands for Acquired Immuno Deficiency Syndrome is a syndrome caused by the HIV virus. It is mainly transmitted through sexual intercourse, blood transfusions and sharing needles.

All of these are related to mosquito bite.

Most of the mosquitoes lay their eggs or mainly breed in standing water. The common house mosquito is the breed which carries the West Nile virus, and requires only an inch of standing water to lay its eggs.

Down's syndrome, colour blindness and sickle cell anaemia are hereditary diseases.

Jaundice is a disease which affects liver. Peptic ulcer is caused by Helicobacter pylori. Colour blindness is a congenital disease.

Among the above listed diseases, common cold has the shortest effect on an individual's health. A healthy man suffers from common cold due to some viruses which stay in the human body for hardly 5-6 days.

Non-communicable diseases are those diseases which cannot be transferred from one individual to another. So, cancer is a non-communicable disease.

Polio is caused by poliovirus. Poliovirus, the causative agent of poliomyelitis (commonly known as polio), is a human enterovirus and member of the family Picornav.

Hepatitis is a disease which affects or causes an inflammation of the liver. Hepatitis virus is the main cause of hepatitis.