Microorganism News

What is the mechanism of virus transmission through blood?

When exposed to the blood of others you need to be very careful, because some viruses are transmitted through the blood. But why some virus transmit in this way, and how does the virus spread it from person to person?

The spread of the virus

Virus is a non-living infectious agent, which can use the body cells to complete reproduction and proliferation, unlike bacteria or fungi, it can’t do this on its own, and must find the appropriate host cells to grow and reproduce.

When the blood-borne viruses reach a certain level, they can be detected in the infected person’s blood. These viruses can move from person to person by blood, in some cases, they can also spread through the body fluids, such as semen and breast milk. The blood-borne virus can also be passed by intravenous drugs use, as well as transmitted from the mother to the child, before, during or even after birth.


For human health, the most important blood-borne viruses are HIV, hepatitis B virus and hepatitis C virus; these viruses can persist in the body’s blood for a long time and even for life. Researchers also found a brief appearance of certain viruses in individual blood, but in general these viruses were not persistent and were not considered to be significant blood-borne pathogens. Any infectious agent with a blood-borne, or “viraemic” phase has the potential for blood borne transmission, so this may be very important for blood transfusions.

For many infectious diseases, the virus infection period will continue until the body’s immune system starts to kill all infected cells and make the infection to be cured; For some viruses, including Zika and Dengue, the virus infection period will last for several days, and for other viruses such as hepatitis B virus, hepatitis C virus and HIV, the virus infection will continue to exist.

The treatment of blood-borne diseases aims to block the replication of the virus. If the blood-borne virus can not be detected in the patient’s blood, then generally the patient is considered as not contagious.

How does the virus transmit through the blood?

HIV infection can occur when an individual is exposed to HIV virus, and the infection usually involves sexual contact or direct blood contact, either through an open wound or penetration of skin by a contaminated needle. Then the virus will enters to the body’s lymph nodes, then gets into the cells of the immune system called T cells. Then comes the “cat and mouse war”. The virus and immune system will use complex strategy to fight against each other until one party was defeated.

Perhaps the greatest of these tricks are from HIV, which incorporates itself into the DNA of the host T cells so that it is hidden in the protected sites from immune system, such as the central nervous system; this makes the body unable to clear the HIV virus completely, and if the patient is not effectively treated, then the virus can still be detected in the patient’s blood. The cells responsible for attacking the virus will produce new virus particles, and attack other infected T cells; if not treated the patients ‘ immune system will be destroyed, and some rare infections or a syndrome called immunodeficiency syndrome (AIDS) are almost fatal to the patient.

In contrast, the influenza virus spreads through the respiratory droplets. When the infected individuals cough or sneeze, the virus particles will be spread; when the droplets are inhaled by a new host, the virus will bind to target receptors on the respiratory tract surface, and replicate in the cells of the respiratory tract.

Unlike HIV, the influenza virus can not insert itself into the host’s gene, so the body’s immune system can detect the infection, shut down viral reproduction, while clear the infected cells. The medications can help this process, but they are usually unnecessary, as the body’s immune system is usually ble to cure influenza independently. Previous influenza infection or vaccination will provide the body some immune memory, and also provide protection and faster immune clearance of the virus.

When the individual exhibits flu-like symptoms, the influenza virus can be found in the body’s blood in a very short time, especially in very serious disease cases. Although bloodstream infections are usually not tested for influenza virus infection, blood donation is often not recommended if blood donors are uncomfortable and have flu-like symptoms.