Pathogens and how disease spreads
A microorganism that causes disease is called a pathogen. Pathogens spread through the air (coughs and sneezes), through contaminated food and water, by direct contact, and through vectors such as mosquitoes. Diseases such as tuberculosis, dengue and influenza are all caused by microorganisms, so preventing their spread is a key part of staying healthy.
The body's defences
The body defends itself in stages. The skin is the first line of defence, acting as a physical barrier that keeps pathogens out. Acid in the stomach and mucus in the airways also trap or destroy many microbes before they can do harm. If a pathogen still gets inside, white blood cells engulf and destroy it and produce antibodies that neutralise it.
Prevention: vaccines
A vaccine contains weakened, dead or harmless parts of a pathogen. When it is given, the body is stimulated to make antibodies without becoming seriously ill. This produces active immunity, so if the real pathogen attacks later, the body can fight it off quickly. Vaccines protect against diseases such as measles, polio and tuberculosis. In Malaysia, babies are given a schedule of vaccinations from birth so that the whole community builds up protection together.
Key idea
A vaccine trains the body in advance: it triggers antibody production so the person becomes immune before meeting the real, dangerous pathogen.
Treatment: antibiotics
Antibiotics are medicines that kill or stop the growth of bacteria. They do not work against viruses, so they cannot cure a cold or flu. Taking antibiotics carelessly — for example, not finishing the full course — allows some bacteria to survive and leads to antibiotic resistance, making infections much harder to treat.
Remember
Simple habits prevent most infections: wash your hands, keep food and water clean, cover your mouth when coughing, and keep up to date with vaccinations.