It is a type of communicable or infectious disease caused by some germs. These germs somehow must reach a new healthy person before he can suffer from the disease. The cause of the disease is called pathogen and its transmission from one person to another is called infection. Other common infectious diseases are cholera, malaria, etc.

Arthritis is a form of joint disorder that involves inflammation of one or more joints. The most common form of osteoarthritis (degenerative joint disease) is a result of trauma to the joint, infection of the joint or age. Other arthritis forms are rheumatoid arthritis, psoriatic arthritis, and related autoimmune diseases. Septic arthritis is caused by joint infection. Schizophrenia is a mental disorder characterised by a breakdown of thought processes and by poor emotional responsiveness.

Cholera is an infection of the small intestine that causes a large amount of watery diarrhea.

When there are scattered cases of a disease, they are called sporadic. Malaria and cholera are the diseases belong to this category.

Tetanus is an infection of the nervous system with the potentially deadly bacteria Clostridium tetani.

Pneumonia is an infection of the lungs that is caused by bacteria, viruses, fungi, or parasites.

Whooping cough (pertussis) is an infection of the respiratory system caused by the bacterium Bordetella pertussis. DPT refers to a class of combination vaccines against three infectious diseases in human; diphtheria, pertussis (whooping cough) and tetanus. The vaccine components include diphtheria and tetanus toxoids, and killed whole cells of the organism that causes pertussis.

Airborne droplet nuclei develop when the fluid of pathogenic droplets (1 to 5 m in size) evaporates. They are so small and light, and they may remain suspended in the air for several hours. Thus, they may also infect persons entering a room which has been left by a patient long ago.

Syphilis is a highly contagious disease spread primarily by sexual activity. It infects the genital area, lips, mouth or anus of both men and women.

Infection is the invasion of a host organism's bodily tissues by disease causing organisms.

Taeniasis is a form of tapeworm infection, which is caused by tapeworms of the genus Taenia. In humans, the mode of transmission is by the ingestion of undercooked beef or pork containing the larval cysts.

Mumps is a virus that can lead to swelling and pain in the salivary glands along with fever, loss of appetite and fatigue.

A characteristic marker of measles are koplik's spots, small red spots with blue white centers that appear inside the mouth.

Rabies is a viral disease that causes acute encephalitis in warm blooded animals. Negri bodies are eosinophilic sharply outlined pathognomonic inclusion bodies found in the cytoplasm of certain nerve cells containing the virus of rabies especially in Ammon's horn of the hippocampus. It is also found in the cerebellar cortex of postmortem brain samples of rabies victims. They consist ribonuclear proteins produced by the virus.

The virus particle consists an outer lipid envelope and an icosahedral nucleocapsid core composed of protein. These virions are 42 nm in diameter and are sometimes referred to as Dane particles. This is known as the Dane particle as it was discovered by Dane in 1970. The nucleocapsid encloses the viral DNA and a DNA polymerase that has reverse transcriptase activity.

The varicella vaccine is a live (attenuated) virus that protects against the viral disease commonly known as chickenpox caused by the varicella zoster virus (VZV). The varicella vaccine is marketed as varivax in the U.S and globally as varilrix by glaxosmithkline. Another vaccine that is known as Zostavax is simply a larger than normal dose of varivax, and is used to reduce the risk of shingles also called herpes zoster and postherpetic neuralgia that are caused by the same virus.

Warts are small usually painless growths on the skin caused by a virus called human papillomavirus (HPV). A wart is generally a small rough growth typically on a human's hands or feet but often other locations that can resemble a cauliflower or a solid blister.

Scarlet fever is a disease caused by infection with the group A Streptococcus bacteria. This bacterium will produce a toxin that leads to the hallmark red rash of the illness.

Leprosy is also known as Hansen's disease (HD). It is a chronic disease caused by the bacteria Mycobacterium leprae and Mycobacterium lepromatosis.

Convalescent carrier is a person who has recovered from the symptoms of an infectious disease but is still capable of transmitting pathogens to others. Persons in this category are the most frequent source of infection for others.

HIV-1 virus is made up of protein envelope and two copies of single stranded RNA of the genome. The envelope contains 72 external spikes. This spike is made up from the glycoproteins GP120 and GP41. Here GP stands  for glycoprotein and the number refers the mass of protein. GP120 is present in external spike and GP41 is in transmembrane.

Erysipelas is a bacterial skin infection involving the upper dermis that characteristically extends into the superficial cutaneous lymphatics. It is usually caused by group A Streptococcus bacteria.

Chicken pox is a highly contagious disease caused by primary infection with varicella zoster virus (VZV). It usually starts with vesicular skin rash mainly on the body and head rather than at the periphery, and becomes itchy, raw pockmark which mostly heal without scarring.

Mite is a term commonly used to refer a group of insect like organisms, some of which bite or cause irritation to humans. Scabies is an easily spread skin disease caused by a very small species of mite. Symptoms of this disease are itching (especially at night), rashes (especially between the fingers) and sores (abrasions) on the skin from scratching and digging.

Streptomycin is the first antibiotic drug of a class of drugs called aminoglycosides and it was the first antibiotic remedy for tuberculosis.

Black piedra is a superficial fungal infection of the hair shaft caused by Piedra hortae forming hard black nodules on the shafts of the scalp, beard, moustache, and pubic hair.

Coccidioidomycosis or valley fever is an infection that occurs when the spores of the fungus Coccidioides immitis enter your body through the lungs.

Trichomoniasis is a sexually transmitted infection caused by the parasite Trichomonas vaginalis. It is sometimes referred to as trich and a common cause of vaginitis.

Q fever is a disease caused by infection of Coxiella burnetii, which is a bacterium that affects humans and other animals. The infection results from inhalation of a spore like small cell variant and from contact with the milk, urine, feces, vaginal mucus or semen of infected animals.

Athlete's foot, also known as ringworm of the foot, or tinea pedis, is a fungal infection of the skin that causes scaling, flaking and itch of affected areas. It is caused by fungi in the genus Trichophyton. The fungus genus Trichophyton is characterized by the development of both smooth walled macro and microconidia. Trichophyton rubrum is a fungus that is the most common cause of athlete's foot, jock itch and ringworm.