Why does the human body become infected by viruses?

The human body is a complex whole, similar to the function of a machine, which requires the coordinated action of all parts to work in unison. However, the human body is very fragile and can be easily affected by various diseases and cause more serious problems. For example, viral infection is an important cause affecting people's health. Why can the human body be infected by viruses? Let’s take a look at the explanation below, I hope everyone can understand it.

The main types of viral infections are as follows:

1. Respiratory tract

Air droplets containing the virus are inhaled into the respiratory tract through the mouth and nose. Influenza virus, adenovirus, measles virus, etc. are transmitted through this route.

2. Digestive tract

Feces containing the virus are spread through contaminated water, food, utensils, hands and flies, and enter the digestive tract through the mouth. Viruses transmitted through this route include hepatitis A virus and rotavirus.

3. Skin

The virus enters the human body through skin injuries, injection sites, arthropod bites, and animal bites. Viruses transmitted through this route include rabies virus, hepatitis B virus, HIV, and insect-borne viruses.

4. Eyes, mouth, and urogenital tract

Secretions containing the virus come into direct contact with these parts (such as vaginal intercourse, oral sex, hand-genital-oral contact, etc.), causing infection. Viruses that are infected through these routes include herpes simplex virus, adenovirus, HIV, etc.

5. Placenta

The virus infects the fetus through the placenta from the mother. Such as rubella virus, cytomegalovirus and hepatitis B virus.

type

1. Latent infection (subclinical infection). Most viral infections are latent infections.

2. Overt infection. A few viral infections are overt infections. Overt infection can be divided into two types: acute infection and persistent infection.

(1) Acute infection develops rapidly and progresses rapidly, with the course of the disease generally lasting from several days to several weeks. Except for a few who died or developed sequelae in the acute phase, most cases eventually recovered as the virus was cleared from tissues and organs.

(2) Persistent infection: The virus exists in the host for a long time, which can last for months to years, causing chronic persistent infection, which can be divided into the following three types: ① Latent infection. ②Chronic infection. ③ Lentivirus infection.