How long does a virus stay active in the blood?

Anthony L. Komaroff, MD
Internal Medicine
The answer to your question is: it depends on the kind of virus you're talking about.

Whenever any virus invades our bodies, our immune system starts to attack it. Most of the time, our immune system is able to completely get rid of the virus. The immune system also develops a "memory" of the virus. So the next time the same virus invades our body, the immune system attack is even more effective.

So for most viruses, the answer to your question is: not long. Within days or weeks, most viruses are gone from our blood. And from everywhere else in our bodies.

But some viruses can "hide" inside certain cells in our bodies, and avoid being totally removed by the immune system. Some viruses can do this for a long time. Some can even cause a permanent, life-long infection.

Fortunately, many viruses that can cause a life-long infection stay "asleep" inside our cells — not making copies of themselves, and not causing any illnesses.

An example is the Epstein-Barr virus. Over 90% of adults in the U.S. have been infected with this virus, usually before young adulthood. Some people get infectious mononucleosis ("mono") when they first get infected with this virus. Others just get the symptoms of the common cold. And others don't get any symptoms at all. But regardless of the symptoms, the virus stays in certain white blood cells, cells in the throat, and possibly elsewhere — for the rest of our lives. Now and then, it can cause serious diseases. But almost always, it never causes any trouble.
Harvard Medical School The Truth About Your Immune System

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Harvard Medical School The Truth About Your Immune System

Can you boost immunity? Will vitamins, herbs, or probiotics help your immune system fight off disease? What about diet and exercise? Your immune system is your most powerful protector but don't fall...

Continue Learning about Viral Infections

Viral Infections

Viral Infections

Viral infections like herpes simplex, respiratory syncytial virus (RSV), chicken pox and rotavirus are infections caused by a virus instead of a bacterium. Viral infections do not respond to antibiotics, but some specific viruses ...

like influenza A and B can be treated with certain antiviral medications. Most commonly, treatment for viral infections includes drinking lots of fluids, getting rest, eating well and letting the illness run its course.

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.