Because biological agents can survive for different periods of time outside the human body, their locations and modes of action in the human body vary, all of these affect the process of infection. In order to survive and reproduce, such pathogenic microorganisms must have infectious properties. Each infectious agent usually has a specific mode of transmission. For example, some bacteria or viruses can cause changes in the mucosal surface of the respiratory tract of the host through the respiratory pathway, and stimulate nerve reflexes to cause symptoms such as coughing or sneezing, so as to return to the air and wait for the next host. But others cause digestive abnormalities, such as diarrhea or vomiting, and spread with the excretion. In these ways, replicating pathogens can spread widely, depending on the patient’s range of activity.
1. Airborne infection
Some pathogens are freely dispersed in the air, usually 5 microns in diameter, and can float in the air for long periods of time and travel long distances. They are mainly infected by the respiratory system, and are sometimes confused with droplet infection.
2. Droplet infection
Droplet infection is the main route of transmission, many original infection by patients when they cough, sneeze, talk, spewing, warm and humid droplets adhere to the pathogen, along with the air skirts, short, short time to floating in the wind, the next host due to breathing, mouth, or accidentally touch the eye surface adhesion, cause new infected host. Examples: bacterial meningitis, chicken pox, common cold, influenza, mumps, tuberculosis, measles, Rubella, whooping cough and so on. Because the droplet quality and quantity are small, it is difficult to carry heavy pathogens, so parasitic infection is almost not transmitted to other individuals through this way.
3. Fecal-oral infection
It is common in developing countries where health systems are not yet sound and education advocacy is inadequate. Untreated waste water or pathogen contamination directly discharged into the environment may contaminate drinking water, food or utensils touching the mucous membranes of the mouth and nose, as well as incomplete cleaning after toilet use, which may lead to infection of the ingerers through the dietary process. The main pathogens can be viruses, bacteria and parasites, such as cholera, hepatitis A, poliomyelitis, rotavirus and toxoid infection. It can also happen in developed countries. In some cases, organisms may become infected by contact with the feces of a patient because the surface tissue is not sufficiently constructed to protect the individual. It’s not something that normally happens in human populations.
4. Contact contagious
Transmission by direct contact is called contact transmission. In addition to touching and kissing the patient directly, such diseases can also be spread by sharing personal equipment such as toothbrush, towel, razor, tableware and clothing, or by leaving pathogens in the environment after the patient touches them. Such infections are more likely to occur in places where things can be inadvertently shared, such as schools and the military. For example: fungal infection of beriberi, bacterial infection of pus, virus in the epidermis caused by hyperplasia of warts; Syphilis, on the other hand, is a special case, usually caused by healthy individuals coming into contact with an infected chancre.
Sexually transmitted diseases include any disease that can be transmitted sexually and are therefore a form of contact transmission. Because the AIDS epidemic is so serious in the world, it is sometimes discussed independently in medicine. Sexually transmitted diseases (STIs) are usually primarily bacterial or viral infections transmitted to sexual partners by pathogens carried in mucous tissue, semen, vaginal secretions or rectum that have direct contact with the genitals. If there are wounds in these areas, the pathogen may spread a blood infection throughout the body.
5. Vertical transmission
Vertical transmission refers specifically to diseases that the fetus gets from the mother. Latin for “in utero,” said “a form of transmission in the womb”, usually through the mode of infection disease pathogen of fetus, many with viruses and high activity small parasite is given priority to, can be transmitted via blood, or have the ability to through the tissue or cell, thus can spread through the placenta in the mother and son, such as AIDS and hepatitis B. Although bacteria are less common in vertical infection, syphilis can be contracted during childbirth due to contact of the mucous membrane of the fetus or the eye with infected mucous tissue of the mother’s vagina. And a small number of cases are in lactation through milk secretion infection newborn. The latter two routes also fall under the category of vertical infection.
6. Blood transmission
Transmission of disease to another individual, primarily through blood or wound infection, is a blood-borne infection. Common in medical use of injection equipment, blood transfusion technology negligence. Therefore, many medical institutions require that the relevant medical procedures must be carried out through multiple and multiple verification so as not to harm patients, and that the physiological conditions of donors and recipients should be further examined during blood donation and transfusion to reduce the risk of such infections. But because of drug use, needle sharing can lead to hard-to-prevent infections, especially AIDS.
Respiratory infections: influenza, tuberculosis, mumps, measles, whooping cough, etc. (airborne).
Infectious diseases of digestive tract: ascariasis, bacillary dysentery, hepatitis A, etc. (spread by water and diet).
Blood infectious diseases: hepatitis B, malaria, epidemic Encephalitis B, filariasis and so on (biological vector transmission).
Surface infectious diseases: schistosomiasis, trachoma, rabies, tetanus, gonorrhea, etc. (contact transmission).
