What Are the Different Types of Viral Infections?

Viral infection (viral infection) refers to the process by which viruses invade the body through multiple channels and multiply in susceptible host cells. Human virus refers to a virus that can infect or cause disease to humans. The essence of viral infection is the process of interaction between virus and body, virus and susceptible cells. Viral infections often result in varying degrees of injury or viral disease depending on the type of virus and the state of the body. Viral pathogenicity begins by invading the host and infecting cells, and the pathogenic effect is manifested in both human and cellular aspects.

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Viral infection (viral infection) refers to the process by which viruses invade the body through multiple channels and multiply in susceptible host cells. Human virus refers to a virus that can infect or cause disease to humans. The essence of viral infection is the process of interaction between virus and body, virus and susceptible cells. Viral infections often result in varying degrees of injury or viral disease depending on the type of virus and the state of the body. Viral pathogenicity begins by invading the host and infecting cells, and the pathogenic effect is manifested in both human and cellular aspects.

English name

virus infection

Visiting department

Infectious Diseases

Contagious

Have

way for spreading

Respiratory tract, digestive tract, urogenital tract, skin wounds, blood, mother and baby, etc.

Virus infection

Horizontal transmission

Horizontal transmission refers to the transmission of the virus between different individuals in the population, including the transmission of the virus from animals to humans. The common horizontal transmission methods are as follows.

(1) Transmission through the respiratory tract: The virus is inhaled through the air, droplets and other infections, such as influenza virus and rubella virus.

(2) Transmission through the digestive tract: The virus contaminates food and water sources, and is infected by ingestion. Such as hepatitis A virus, polio virus and so on.

(3) Transmission through genitourinary tract: infections caused by direct sexual contact, such as human immunodeficiency virus, herpes simplex virus, etc.

(4) Transmission through skin wounds: Infections caused by insect-borne bites, animal bites, or direct contact of skin wounds with the virus. Such as epidemic encephalitis virus, rabies virus and so on.

(5) Transmission through blood: infections caused by blood transfusion or blood products, including injection, organ transplantation, etc., such as hepatitis B virus, human immunodeficiency virus, etc.

2. Vertical propagation

The way the virus is transmitted from mother to fetus or newborn through the placenta, birth canal, and lactation is called vertical transmission. Vertically transmitted viruses include rubella virus, human immunodeficiency virus, and hepatitis B virus.

Virus infection

After being infected with the virus, the body can show different clinical types. According to the presence or absence of symptoms, it can be divided into dominant infection and recessive infection; according to the virus retention time and the duration of symptoms, it can be divided into acute infection and persistent infection.

Recessive infection

Because the number of viruses invading the body is small, the virulence is weak, or the body's resistance is strong, the virus proliferates in the host cell, but the body does not show obvious clinical symptoms, which is called recessive infection. A recessive infection allows the body to acquire specific immunity to the virus and protects the body from re-infection by the virus. Recessive infections do not show clinical symptoms, but the virus still proliferates in the body and spreads the virus to the outside world, becoming an important source of infection.

Dominant infection

Due to the large number of viruses invading the body, the strong virulence or the weak resistance of the body, the virus proliferated in the host cells in large numbers, and obvious clinical symptoms appeared, which are called dominant infections. Dominant infection depends on the duration of the infection. Divided into acute infection and persistent infection.

(1) Acute infection: After the virus invades the body, the incubation period is short, the onset is acute, and the course of the disease is several days to several weeks. Specific immunity is often obtained after the disease. The body can completely remove the virus from the body through its own immune mechanism, such as Hepatitis A virus.

(2) Persistent infection: After the virus invades the body, it persists in the body for months, years, or even decades, and the body can appear clinical symptoms, or it can carry the virus for a long time without clinical symptoms, becoming an important source of infection. Persistent infection can be divided into three types according to the course of disease and pathogenic mechanism. Chronic infection: After the virus invades the body, it exists in the blood or tissues for a long time, and the body may or may not have symptoms. Viruses can be detected throughout the course of the disease, such as chronic hepatitis caused by hepatitis B virus. Latent infection: After the primary infection, the virus genes dormant in certain tissues or cells of the body, but do not replicate and proliferate infectious viruses. At this time, the body has no clinical symptoms and does not excrete the virus to the outside. The virus can be activated for acute attacks under certain conditions, and viruses such as herpes simplex virus can be detected. Slow-onset virus infection: After a dominant or recessive infection, the virus is dormant in the body for a long time, and the incubation period can be as long as several months to several years. At this time, the body is asymptomatic and the virus cannot be detected. Once onset, it is subacute and progressively exacerbates until death, such as human immunodeficiency virus infection.

Pathogenesis of virus infection

1. The direct effect of the virus on the host cell

Different types of viruses interact with host cells and can exhibit different forms. In addition to stopping infection after entering into non-containing cells, it can also be manifested as cytolytic infection, stable infection, apoptosis, cell proliferation and transformation, integration of viral genes, and formation of inclusion bodies.

2. Immunopathological effects of viral infection

Tissue damage caused by immunopathology is common in viral infections. In addition to viruses, there are also autoantigens that arise from viral infections in addition to viruses. In addition, some viruses can directly invade immune cells and destroy their immune function.

Virus infection check method

Viral infections are very common. Examination of viral infections is not only used for the evaluation of clinical diseases, but also for epidemiological investigations, providing a scientific basis for the prevention and treatment of viral diseases.

Optical microscopy

With a light microscope, large single virions such as poxviruses can be directly observed, and inclusion bodies in tissue cells infected by some viruses can also be directly checked.

2. Electron microscopy

Electron microscope direct inspection: used to directly detect related virus particles, such as herpes virus, hepatitis A virus, and hepatitis B virus particles, from herpes fluid, stool or serum samples. Immunoelectron microscopy: The virus specimens are made into suspensions, mixed with specific antibodies, and the virus particles in the specimens are agglomerated into aggregates. The electron microscope inspection can improve the detection rate.

3. Virus isolation and culture

The methods of laboratory isolation and culture of virus include tissue cell culture, animal inoculation and chicken embryo culture.

4. Virus antigen antibody check

Commonly used methods include neutralization test, hemagglutination inhibition test, immunodiffusion test, and detection techniques such as fluorescein, enzyme, and radionuclide.

Viral infection

Currently, there is no effective drug treatment for most viral infections, so artificial immunity is the most effective way to prevent viral infections.