Mechanisms of Disease Transmission 1.1 Concept of Disease Transmission A healthy person, as a potential host in society, may be infected with a certain infectious disease according to his position in society and the influence of various reservoirs around him. This possibility is also greatly influenced by various factors, including: a) Surrounding physical environmental factors which are media that influence the quality and quantity of causal elements. b) Biological environmental factors that determine the types of disease vectors and reservoirs as well as biological elements that live and exist around humans c) Social environmental factors, namely the population of each person in society, including living habits and daily activities. 1.2 Portal Of Exit The agent cannot leave the host's body alive, if the body cannot kill it, either with the help of perfect medication or on its own strength, then transmission cannot take place. This method is an effective control, because if the agent is gone, the disease will disappear. , and an outbreak is unlikely. However, there are many agents that cannot be treated completely. Malaria parasites, for example: (1) After treatment there are often still parasites remaining and taking refuge in the liver cells so that drugs cannot penetrate without causing harm to the sufferer. (2) Reinfection occurs because there are still many sources and spreaders of the disease around the sufferer. There are also various kinds of viruses and bacteria for which there is currently no cure, so the body itself must be strong enough to kill them or the treatment is not perfect, for example the sufferer is unable to pay for the entire amount of medication needed, or does not understand the methods of complete treatment, So after recovery the sufferer still carries bacteria or viruses which are usually referred to as carriers, at certain times these carriers can release agents into the environment through their portal of exit. 1.3 Survival viability The resistance of agents outside the host body varies greatly. Spirochaetes that cause syphilis and gonococcus that cause gonorrhoea have difficulty surviving outside the body, so they can only be transmitted directly from sick people to others. On the other hand, salmonella typhi can survive for quite a long time and even reproduce in food, for example tetanus and anthrax bacillus can survive for years because they can form spores. The spore form is not dangerous for humans, but once the spores enter a favorable environment, meaning there is temperature, nutrients and humidity that are suitable for life, the spore form can change back into a vegetative form and reproduce 1.4 Portal of entry The ability of an organism to cause disease in a host is called pathogenicity. This pathogenicity differs for the type of host and for the type of organism. Of course, culture development can only occur if the potential host cannot defend against the agent. As is known, in the host's body, living agents generally give rise to what are called antibodies against the agent because they have a structure antigenetic. Once the host forms antibodies, the agent has the ability to form similar antibodies more quickly and in greater abundance in subsequent infections. 1.5 Cultural Durability Cultural resilience can be obtained from community culture, such as: 1) Knowledge that a disease can be prevented by immunization can prevent the occurrence of infectious diseases. Even if the agent manages to enter the body, because the host is immune to the incoming agent (due to immunization), if disease occurs later, the host will not suffer as badly as those who do not receive immunization. 2) Knowledge about the environment that can spread disease and become a disease vector, makes humans maintaining the quality of the environment which will minimize the transmission of disease. 3) Knowledge about the role of nutrition in the body's defense and if people try to maintain good nutrition, it will minimize the incidence of disease. 1.6 Chain of Infection There is a close relationship between the epidemiological triangle and the chain of infection. Disease transmission occurs when a pathogen or egan leaves the reservoir through a portal of exit and is spread by one of the transmission methods. Pathogens or agents that cause disease enter the body through a portal of entry and infect the host if the host is susceptible. The etiological pathogen chain includes bacteria, viruses, worms, chemicals, or animal or plant substances or other factors that can cause disease, disability, illness, syndrome, or death. Once the egan or pathogen leaves the reservoir, the agent using a transmission method will move to a susceptible host, either through direct transmission (person-to- person contact) or indirect transmission (droplets, or airborne dust particles, vectors, fomites, food substances). The final link in the chain of infection is a susceptible individual or host, usually a human or animal. The host is generally protected from pathogen attacks by the skin, mucous membranes,and physiological responses (eg, tears to clean the eyes, acidity in the stomach, cilia in the respiratory tract, and the response of the body's immune system). If the pathogen can enter the host's body, the result will most likely be illness if the host does not have immunity to the pathogen.