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| What are the transmission routes of infectious diseases? What is the way of communication? |
Sources of infection In humans, there are pathogens that grow and reproduce, and humans and animals that can be discharged from pathogens, that is, people and animals that are infected with infectious diseases or carry pathogens. Patients with infectious diseases are an important source of infection and have a large number of pathogens in their bodies. At various stages of the disease, the patient's source of infection has a different effect, which is mainly related to the number of diseases, the number of pathogens discharged, and the extent and frequency of contact between the patient and the surrounding population. For example, most patients with infectious diseases can discharge a large number of pathogens when they have clinical symptoms, which threaten the surrounding population and is an important source of infection. However, some patients, such as whooping cough, have more pathogens in the catarrhal period and are highly contagious. However, the number of pathogens discharged during the cough period is significantly reduced, and the infectivity is gradually reduced. Another example is that hepatitis B patients are contagious at the end of the incubation period.
Generally speaking, the patient is no longer a source of infection during the recovery period, but the recovery period of some infectious diseases (typhoid, diphtheria) can still discharge the pathogen within a certain period of time and continue to function as a source of infection.
A pathogen carrier is a person or animal that has no clinical symptoms but is capable of expelling the pathogen. Carriers have both carriers and so-called healthy carriers. The former refers to individuals whose clinical symptoms disappear and the body functions recovery, but continue to discharge pathogens. This type of carrying state generally lasts for a short period of time, and a small number of individuals carry a long time, and individual ones can last for many years, such as chronic typhoid carriers. The so-called healthy carriers have no history of disease, but they can be found to have pathogens in their discharges by inspection. The time for such people to carry pathogens is generally short-lived.
Diseased animals are also a source of infection for human infectious diseases. People are infected by bites or secretions from diseased animals (such as rabies, rat biting fever) or exposure to diseased animals.
Humans and animals can suffer from the same disease, but pathological changes, clinical manifestations, and significance as sources of infection are not the same. If a dog with rabies can appear to attack people and other animals, it becomes one of the sources of infection of the disease, and the clinical manifestation of the disease is water-induced disease, which no longer becomes the source of infection.
Path of transmission refers to the way in which the pathogen is carried out in the external environment before being transmitted to another susceptible person after being discharged from the source of infection. The transmission route of an infectious disease can be single or multiple. The route of transmission can be divided into two categories: horizontal transmission and vertical transmission.
Since biological pathogens can survive in vitro for different periods of time, there are differences in the location and activity patterns in the human body, which affect the process of how an infection is transmitted. In order to survive and reproduce, such pathogenic microorganisms must be infectious, and each infectious agent usually has a specific mode of transmission, such as through the path of breathing, certain bacteria or viruses can cause the surface of the host's respiratory tract. The type of mucous membrane changes, stimulates nerve reflexes and causes symptoms such as coughing or sneezing, thereby returning to the air to wait for the next host to enter, but some microorganisms cause abnormalities in the digestive system, such as diarrhea or vomiting. The discharge is scattered everywhere. In these ways, the pathogens that are replicated can be spread in large numbers along with the patient's range of activities.
Susceptible population refers to the degree of susceptibility or immunity of a population to a certain infectious disease pathogen. The increase in the number of new students, the concentration of susceptible people or entering the epidemic areas, the recruits of the troops recruited, easily lead to epidemics. Immunization after the disease, hidden infections of the population, and artificial immunization all reduce the susceptibility of the population, and it is not easy to spread the epidemic or terminate its epidemic.
Airborne infection
Some pathogens are free to spread in the air, usually 5 microns in diameter, can float in the air for a long time, and move long distances, mainly through respiratory infections, sometimes mixed with droplets.
Droplet infection
Droplet infection is the main route of transmission for many infectious agents. When the patient coughs, sneezes, and speaks, it sprays warm and moist droplets. The pathogen attaches to it and drifts with the air for a short time and short distance in the wind. Floating, when the next host adheres to the surface of the eye by breathing, opening mouth or accidentally, causing the new host to become infected. For example: bacterial meningitis, chickenpox, common cold, influenza, mumps, tuberculosis, measles, German measles, whooping cough, etc. Because of the small amount of droplets and the small amount, it is difficult to carry a heavier pathogen, so parasitic infections rarely infect other individuals by this route.
Fecal infection
It is common in the case that the health system in developing countries is not yet sound and the education is not well-conceived. Untreated wastewater or contaminated materials are directly discharged into the environment, which may contaminate drinking water, food or utensils that touch the mouth and nasal mucosa. And incomplete cleaning after going to the toilet, the diet can lead to infection of the ingestion, the main pathogens can be viruses, bacteria, parasites, such as cholera, hepatitis A, polio, rotavirus, toxoplasmosis ( T. gondii) may also occur in developed countries. Sometimes, some organisms are not adequately protected by the body surface structure, and may be infected by contact with the patient's excrement. Normally, this special case does not occur in the human population.
Contact infection
The way of infection through direct contact is called contact infection. In addition to directly touching and kissing patients, these diseases can also be shared by toothbrushes, towels, razors, tableware, clothing, etc., or after patient contact. Leave the pathogen in the environment to achieve the purpose of transmission. Therefore, such infectious diseases are more common in places where schools, military and other items may be inadvertently shared. For example: Hong Kong foot of fungal infection, Impetigo of bacterial infection, sputum caused by virus in the epidermis, and syphilis is special, usually caused by the hard chancre of healthy individuals.
Sexually transmitted diseases contain any disease that can be transmitted through sexual behavior. Therefore, they are a type of contagious infection. However, because AIDS is very prevalent in the world, it is sometimes discussed independently in medicine. Usually the main infection is a bacterium or a virus, which is transmitted to a sexual partner to cause infection by direct contact with the mucosal tissue of the genitals, semen, vaginal secretions or even the pathogens carried by the rectum. If there are wounds in these areas, the pathogen may bring blood infections throughout the body.
Vertical infection
Vertical infection refers to the disease that the fetus receives from the mother. Latin uses "in utero" to mean a form of infection in the uterus. It usually infects the disease pathogen of the fetus through this infection. It is mainly caused by viruses and small parasites with high activity, which can be transported through blood. , or have the ability to pass through tissues or cells, so it can be transmitted through the placenta in the mother and child, such as AIDS and hepatitis B. Although microorganisms such as bacteria and fungi are rare in vertical infection, Treponema pallidum can be infected during the delivery process due to contact with the mucosal tissue of the mother's vagina due to contact with the mucous membrane of the fetus; and in a few cases, during lactation Milk secretion from infected newborns. The latter two paths are also in the category of vertical infection.
Blood infection
The process of transmitting the disease to another individual, that is, through blood and wound infection, is blood. Commonly used in medical use of injection equipment, blood transfusion technology, so many medical institutions require the implementation of relevant medical procedures, must be confirmed by multiple, multi-persons to avoid harm to patients, in the blood donation, blood transfusion, but also for donors and recipients Testing related physiological conditions reduces the risk of such infections, but due to the use of drugs, sharing needles can cause unpredictable infections, especially for AIDS prevention.
Respiratory infectious diseases: influenza, tuberculosis, mumps, measles, whooping cough, etc. (airborne)
Digestive tract infectious diseases: tsutsugamushi disease, bacterial dysentery, hepatitis A, etc. (water, diet)
Blood infectious diseases: hepatitis B, malaria, epidemic encephalitis, filariasis, etc. (biological media, etc.)
Surface infectious diseases: schistosomiasis, trachoma, rabies, tetanus, etc. (contact spread)
Sexually transmitted diseases: gonorrhea, syphilis, AIDS, etc.
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