There are innumerable pathogens that differ in name, makeup, disease-causing mechanism, and malignancy. Drugs exist for many of these evildoers – whether to treat sick people or to protect large populations. Bacteria, viruses, fungi are the first that come to mind when we are asked to list pathogens, but there are more – prions that cause BSE, worms (such as the fox tapeworm), and parasites. There are also fleas, mosquitoes and ticks that can be infected with pathogens and transmit them to humans.
Infectious diseases caused by bacteria
Bacteria are tiny living things that are not necessarily harmful. On our skin and in the intestines, there are species that even help us – for example, they produce the protective acid mantle of the skin or break down food pulp. Others, such as meningococci or pneumococci, are very dangerous for the brain and lungs. Helicobacter, Campylobacter and Salmonella are bacteria that like to upset the gastrointestinal tract. It is also known that tubercle bacilli cause consumption and Lyme disease bacteria cause Lyme disease via ticks as carriers.
Infectious diseases caused by viruses
Viruses depend on other living organisms because they cannot live alone. Once a virus has nested and multiplied in a body cell, the host cell breaks down. In the process, many viruses cause annoying but not life-threatening diseases: Cold viruses and diarrhea viruses such as rota or noroviruses are examples. Other viruses cause mononucleosis, influenza, TBE or hepatitis – all diseases that humans can usually handle. More threatening are SARS or avian flu – because without a vaccine, humans are pretty much helpless.
Infectious diseases caused by fungi
There are also differences in fungi: many are harmless, edible or can be used as a remedy. On the other hand, one type of mold is probably responsible for the legend formation “the curse of Pharaoh”. Pathogens, in addition to causing typical infectious diseases, can unfortunately also be carcinogenic – Helicobacter is suspected of causing stomach cancer, molds are thought to promote the development of liver cancer, and the link between papillomaviruses and uterine cancer is certain.
One of the leading causes of death: Infectious diseases
Infectious diseases are among the leading causes of death worldwide, with AIDS, tuberculosis, and malaria accounting for the most deaths. Our immune system constantly takes care of pathogens with which we have contact through skin, breathing and food – since it usually works well, we don’t notice.
Only when our immune system is weakened – because of a congenital immune defect, stress, or another disease like diabetes – do pathogens have a chance. If our immune system underestimates a pathogen, life-threatening sepsis is imminent. Rare, highly virulent pathogens are also important as biowarfare agents: anthrax and smallpox are the focus of terrorist interest.
