Certain infections are caused by harmful microorganisms, such as bacteria, viruses, fungi, or parasites. These pathogens can enter the body through various means, including cuts, inhalation, or ingestion. Common examples include the flu, caused by the influenza virus, and strep throat, caused by the Streptococcus bacteria. Infections can lead to a range of symptoms, from mild to severe, depending on the type and location of the infection. Treatment often involves medications like antibiotics for bacterial infections or antiviral drugs for viral infections. Preventive measures, such as vaccinations and good hygiene practices, can help reduce the risk of infections.