INFECTION
Infection (Latin: infectio) is an invasion of an organism’s body tissues by disease-causing agents, their multiplication, and the reaction of host tissues to the infection. Infectious diseases are caused by pathogenic microorganisms, such as bacteria, viruses, fungi or parasites. These organisms can invade and multiply within humans or other animals causing tissue damage and illness.
The study of infection is called infectious disease epidemiology. Infections are classified according to the causative agent and site affected. The most common types of infections are bacterial infections, viral infections, fungal infections and parasitic infections. Bacterial infections include pneumonia, tuberculosis and meningitis; viral infections include influenza, HIV/AIDS and SARS; fungal infections include candidiasis (thrush) and ringworm; parasitic infections include malaria and schistosomiasis.
Most infectious diseases can be prevented by vaccination or prophylactic measures such as handwashing with soap and water. Some infectious diseases can be treated with antibiotics or antiviral drugs; however, many pathogens are becoming resistant to these drugs making treatment difficult. Infectious diseases place a significant burden on healthcare systems worldwide causing millions of deaths each year.