The route that causes the epidemic and spread of infectious diseases is called the route of transmission, that is, the route through which pathogenic microorganisms are discharged and invade another susceptible organism. Common routes of transmission are: (1) airborne transmission, including (1) droplet transmission. Pathogens existing on the surface of respiratory mucosa can be ejected with the patient exhaling, talking loudly, coughing, sneezing, etc. These mucus droplets containing a large number of pathogens are small in size and suspended in the air for a short time (usually no more than a few seconds), so the spread of droplets is limited to close contacts around patients or carriers. Epidemic cerebrospinal meningitis, influenza and whooping cough can be spread in this way. Crowded public places, such as cabins with many passengers and waiting rooms at stations, are common places where this kind of spread occurs. ② It is spread by dust. Secretions containing pathogens are scattered on the ground, clothes or sheets in large droplets and become dust after drying. When tidying clothes or sweeping the ground, dust with pathogens flies and causes respiratory transmission. All dry-tolerant pathogens can be spread in this way, such as mycobacterium tuberculosis and anthrax spores.
Most airborne infectious diseases have seasonal characteristics, which are generally more common in winter and spring. There are many factors affecting air transmission, which are related to population density, living conditions and the proportion of susceptible people in the population. (2) Water transmission includes two modes of transmission. One is diseases caused by drinking water polluted by feces, such as cholera, typhoid fever, bacillary dysentery and hepatitis A; The other is diseases caused by contact with "epidemic water" (infected water), such as schistosomiasis and leptospirosis, and its pathogens mainly invade the body through skin and mucosa. (3) Through food transmission, all intestinal infectious diseases, some parasitic diseases and individual respiratory diseases (such as tuberculosis and diphtheria) can be transmitted through food. (4) Contact transmission, including two modes of transmission: ① Direct contact transmission refers to the transmission caused by the contact between the source of infection and the susceptible person without any external factors, such as sexually transmitted diseases, rabies, rat bite fever, etc. (2) indirect contact transmission, also known as daily contact transmission, refers to the transmission caused by the contact of susceptible persons with daily necessities contaminated by excreta or secretions from infectious sources. Contaminated hands play a particularly important role in indirect contact transmission.
Sexually transmitted diseases include any diseases transmitted through sexual behavior, which belongs to contact infection. (5) Transmission by vector arthropods refers to infectious diseases transmitted by arthropods biting and sucking blood or polluting food. For example, flies and cockroaches can carry pathogens of intestinal infectious diseases, and mosquitoes can spread Japanese encephalitis. (6) Spreading through soil. There are many opportunities for soil pollution. For example, human manure fertilization pollutes the soil with intestinal pathogens or parasitic eggs, such as hookworm eggs and ascaris eggs. Spores of some bacteria can survive in the soil for a long time, such as tetanus, anthrax, gas gangrene, etc. If the skin is damaged, it can cause infection through the soil; Children playing in the soil are susceptible to ascariasis. (7) Vertical transmission is the transmission between the pregnant woman and the fetus, which can include transmission through the placenta and transmission caused by childbirth.