Key Points

According to the World Health Organization (WHO), health is a state of complete physical, mental, and social well-being, and not merely the absence of disease.

Diseases are categorized into two main types: communicable diseases, which spread from person to person, and non-communicable diseases, which do not spread.

Communicable diseases are caused by pathogens, which are disease-causing organisms like bacteria, viruses, fungi, worms, or protozoa.

Non-communicable diseases like diabetes, cancer, and heart disease are often caused by lifestyle factors, diet, environment, and genetics, not by pathogens.

Pathogens spread through air (coughing, sneezing), contaminated food and water, direct contact, or through insects called vectors, such as mosquitoes and houseflies.

A symptom is something a person feels, like pain or tiredness. A sign is something that can be seen or measured by others, like a fever, rash, or high blood pressure.

Immunity is the body's natural ability to fight diseases. The immune system is the special system that protects the body against harmful pathogens.

Vaccines train the immune system to fight a disease by introducing a weakened, dead, or harmless part of a pathogen. This helps the body develop acquired immunity without causing the illness.

In the late 1700s, English doctor Edward Jenner created the first vaccine for smallpox after observing that people infected with the milder cowpox did not get smallpox.

Antibiotics are medicines that kill bacteria or stop them from growing. They are effective only against bacterial infections and do not work on viruses like the common cold or flu.

Alexander Fleming discovered penicillin, the first antibiotic, in 1928. He noticed that a mould had stopped the growth of bacteria on a petri dish.

Antibiotic resistance happens when bacteria evolve to survive treatment with antibiotics that once killed them. This is a major health threat caused by the overuse and misuse of antibiotics.

A healthy lifestyle involves eating a balanced diet, regular physical activity, getting enough sleep, maintaining hygiene, and avoiding harmful substances like tobacco and alcohol.

A clean environment with clean air and water is crucial for good health. Pollution can cause respiratory problems like asthma and spread diseases.

The traditional Indian system of Ayurveda teaches that true health is a balance of the body, mind, and surroundings. It emphasizes routines, diet, and practices like yoga and meditation.