Infectious disease isProtoplasmIt is a process of discharging from the infected person and invading the susceptible person's body through a certain transmission route to form a new infection, which continues to occur and develop.
The process of epidemic of infectious diseases in the population, that is, the pathogen is discharged from the infected person, invades the susceptible person's body through certain transmission channels, and forms new infections, and continues to occur and develop.The prevalence of infectious diseases among people requires three basic conditions, also known as three links, namelyInfectious agent, transmission route and susceptible population.These three links are interdependent and interrelated. Without any of them, the epidemic of infectious diseases will not occur.[1]
Epidemic focus
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fromInfectious agent(that is, infected people and animals) can spread pathogens to the surrounding areasEpidemic focus。epidemiology
Epidemic focusThe scope depends on three factors, namelyInfectious agentThe scope of activities, the characteristics of transmission routes and the immune status of the surrounding population.
eachInfectious agentCan form a singleEpidemic focusHowever, there can also be more than one infectious source in one epidemic focus.
Epidemic focusThe eradication must meet three conditions:
oneInfectious agentThe state of having been removed (hospitalized or dead) or having eliminated the discharge of pathogens (cured).
2. Eliminated through various measuresInfectious agentPathogens discharged from the external environment.
3. All susceptible contacts have gone through the longest incubation period of the disease without new cases or new infections from the last moment of possible infection.
When these three conditions are metEpidemic focusAll kinds of epidemic prevention measures can be ended.
every lastEpidemic focusIt happens from the focus in front of it, and it can trigger new focus itself. The process of continuous occurrence of a series of focus is calledEpidemic process。Therefore,Epidemic focusIt is an infectious diseaseEpidemic processBase unit of.
Because many infectious diseases existPathogen carrier、Recessive infectionHuman and animal natureInfectious agent, thus collecting infectious diseasesEpidemic processIt can not be completely regarded as the process of occurrence, transmission and termination of infectious diseases (patients) in the population.
Form of expression
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Intensity of popularity
The epidemic intensity of infectious diseases refers to the number of certain infectious diseases in a certain area and in a certain period of time, as well as the strength of contact between cases.The epidemic intensity of infectious diseases can be divided into:
oneemissionThe incidence of a disease is at a general level over the years, and the cases occur in scattered form. The incidence of a disease that has no obvious connection in the time and place of incidence is called sporadic.emissionIt refers to the occurrence of the disease in large areas (counties, cities, provinces and countries).To determine whetheremissionAccording to the comparison between the local incidence rate of the disease in the current year and the incidence rate in the previous three years, if it does not exceed significantly, it can be determined as sporadic.
2. Outbreak refers to the sudden increase in the number of a disease in a short period of time (generally calculated in hours, days, weeks or months) in a certain area.
threeEpidemicIn a region, the incidence of a disease is significantly higher than over the years（emissionIncidence) level (generally 3 to 10 times the average incidence rate of the first three years) is called epidemic.
fourPandemicA disease spreads rapidly in a short period of time, its incidence significantly exceeds the epidemic level of the region over the years, and its epidemic scope exceeds the provincial, national, and even continental boundaries.
For example, cholera in the pastInfluenzaAnd the current worldwide AIDS pandemic.
Distribution form
1. Regional distribution characteristics Infectious diseasesEpidemic processIt often has certain regional characteristics, which are collected by pathogens, insect vectors, and examinationsInfectious agentIt is determined by survival, development and reproduction in a certain external environment.
The disease occurs and spreads at regular intervals, which is calledPeriodicity。The reason for forming the cycle and the length of the cycle interval arePathogen variationAnd peopleimmunityThe result of natural changes.
Population distribution
The population distribution characteristics of infectious diseases mainly depend on the immune level of the population and the opportunity to contact pathogens.If possible due to the increase of the birth population (susceptible children), orimmunityThe emigration, death, migration of people with low immune level, or the relative quiescent period after the epidemic of an infectious disease can all become the influencing factors of the population distribution characteristics of the epidemic of an infectious disease in the local area.[2]
