Infectious diseases are a major health problem worldwide. They are caused by pathogens, which are microorganisms that can invade and cause disease in the host. Pathogens can be bacteria, viruses, fungi or parasites. Infectious diseases can be spread through direct contact with an infected person or animal, by exposure to contaminated food or water, or by inhalation of infectious particles in the air.
Most infectious diseases can be prevented by good hygiene and sanitation practices, vaccination and prompt treatment of infections. Early diagnosis and treatment of infectious diseases is essential to preventing serious illness and death.
There are many different types of infectious diseases, which vary in their severity from mild illnesses to life-threatening conditions. Common examples include influenza (flu), tuberculosis (TB), pneumonia, meningitis and sepsis (blood poisoning). Infectious diseases can also lead to long-term problems such as chronic fatigue syndrome (CFS) or HIV/AIDS.
Infectious diseases are caused by pathogenic microorganisms such as bacteria, viruses, fungi or parasites. These agents enter the body and multiply, causing illness and sometimes death. The route of transmission varies depending on the pathogen involved. For example, viruses are usually spread through contact with respiratory secretions from an infected person (such as via coughing or sneezing), whereas bacteria may be transmitted through contaminated food or water. Some pathogens can also be inhaled into the lungs where they can cause infection (e.g., Legionella pneumophila – the causative agent of Legionnaires’ disease).
Once inside the body, pathogens multiplies and invades different tissues causing damage leading to symptoms typical for a particular infection; for example, inflammation of the lungs in pneumonia or brain damage in meningitis patients . In some cases infection leads to formation of abscesses – localized areas filled with pus that forms when tissue around an infection site is destroyed .
Severe infections may result in sepsis – a potentially life-threatening condition characterized by widespread inflammation and organ dysfunction . Sepsis occurs when chemicals released into the bloodstream during an infection trigger a severe inflammatory response throughout the body . If not treated promptly , sepsis can lead to multiple organ failure and death . Other serious complications associated with some infectious diseases include hepatitis , endocarditis