Infectious diseases require specific pathogens (e.g. hepatitis virus, Mycobacterium tuberculosis)

The biggest characteristics of infectious diseases and the main differences from other diseases → Infectious disease

Infectious diseases that can be transmitted from person to person, animal to animal, or person to animal are called infectious diseases

After overt or latent infection, most people can develop a certain degree of immunity (produce antibodies or sensitize T cells)

The duration of immunity varies, with influenza and bacillary dysentery lasting shorter periods of time; measles, chickenpox, poliomyelitis, etc. generally lasting for life.

a. Seasonality

b. Local

c. Externality

d. Popularity

①Non-specific immunity

②Specific immunity

①Invasion: In layman’s terms, it is the ability to penetrate into human tissue cells

② Toxicity: the ability to damage human tissue, such as toxins that destroy human tissue

③Quantity: For pathogens to cause disease, a certain number is required. The greater the number of pathogens, the stronger their ability to cause disease.

④Variability:

Before the pathogens start to cause disease and infect the human body, they are killed by the body’s immune system → Pathogen elimination

The most common outcome of infectious diseases is latent infection → characterized by asymptomatic and antibody production

People with strong immunity or weak pathogen virulence will cause mild tissue damage and no symptoms after infecting the human body, but stimulate the body to produce antibodies → latent infection

An accidental physical examination revealed that I had not been vaccinated but had developed certain antibodies. However, there are also a small number of people who become pathogen carriers.

For example, adults infected with hepatitis B virus have no symptoms. The final outcome is that 95% of people develop antibodies (hidden infection) and 5% become virus carriers or patients.

The most common and easily identifiable outcome of infectious diseases → dominant infection → characterized by obvious symptoms and the production of antibodies (some long-term, some short-term)

Immunity engages in a fierce battle with pathogens, causing damage to human tissue and causing obvious symptoms. At the same time, antibodies are also produced → dominant infection

There are obvious symptoms, so it is easiest to be discovered by doctors and patients.

Characteristics of pathogen carrying status → Pathogens are present in the body and asymptomatic (pathogens can be excreted and become an important source of infection)

Immunity cannot kill pathogens (pathogens are present in the body), but pathogens do not destroy tissues in large quantities (asymptomatic) →pathogen carrying state

Characteristics of latent infection → Found in some infectious diseases, lurking in specific tissues, developing symptoms only when immunity is reduced, and not expelling pathogens

The pathogen lurks in a specific tissue of the human body. It usually does not cause symptoms and the pathogen is not excreted from the body.

When the body's immunity is reduced, it reproduces in large numbers and causes overt infection, which is only seen in some infectious diseases.

For example, many people have herpes virus latent in the trigeminal ganglion. It usually does not cause blistering on the lips, but it can cause blistering on the lips when staying up late or having a cold with low immunity.