Why are only some viruses transmissible by blood and how are they actually spread?

Blood tests and diagnosing illness: what can blood tell us about what’s happening in our body?
July 28, 2017
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The Conversation – 28th July 2017 

By David Griffin and Thomas Schulz

Since the 1980s, most of us have been aware we need to be careful when coming into contact with the blood of others, because some viruses can be transmitted in this way. But why is it only some viruses are transmissible by blood, and how does the virus actually move from person to person?

Viruses are non-living, infectious agents that use our own cells to function and replicate. Unlike bacteria and fungi, they can’t do this on their own, and must find an appropriate host cell they can enter and replicate in.

Blood-borne viruses are those found at levels that can be detected in an infected person’s blood. They can be passed from person to person by blood, and in some cases other bodily fluids, including semen and breast milk. They can be transmitted from an infected person by intravenous drug use, a needle stick injury with contaminated needles, blood transfusions and sexual intercourse. They can also be transmitted from mother to child, before, during or even after birth.

The most important blood borne viruses for human health are the human immunodeficiency virus (HIV), Hepatitis B and Hepatitis C. These viruses persist in the blood long-term or for life.

Many other viruses may be found briefly in blood, but they generally don’t persist and are not considered significant “blood-borne” pathogens. Any infectious agent with a blood-borne, or “viraemic” phase has the potential for blood borne transmission, and so may be important for blood transfusions.

For many infections, this viraemic period persists until the immune system is able to cure the infection by killing all infected cells. For some viruses, including Zika and Dengue, the viraemic phase lasts a matter of days. For other viruses such as Hepatitis B and C, or HIV, this viraemic phase persists.

Treatment of blood-borne viruses aims to stop the virus replicating. If a blood-borne virus is not detectable in blood, then a person is generally considered non-infectious…

READ MORE AT: https://theconversation.com/why-are-only-some-viruses-transmissible-by-blood-and-how-are-they-actually-spread-75460

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