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Viral Tests

Why It Is Done

A viral test is done to:

  • Find a viral infection that is causing symptoms.
  • Check a person after exposure to a virus. For example, a viral test may be done after a health professional is accidentally stuck with a needle containing contaminated blood to see if he or she became infected with the virus.
  • Find a viral infection in a potential blood donor to prevent the donation of infected blood.
  • Find a viral infection in an organ to be transplanted.
  • Test a pregnant woman who has a high risk of passing a serious viral infection on to her baby.
  • Check if a person has immunity to a specific virus.

How To Prepare

Preparations for a viral test depend on the type of infection that may be present and the sample that will be tested. Your health professional will give you any specific instructions before your test.

How It Is Done

Samples can be collected in several ways.

  • A blood sample can be taken from a vein in the arm.
  • A tissue sample can be taken directly from the infection, such as a throat swab or skin scraping.
  • A sample of stool, urine, or nasal washings may be taken.
  • A sample of spinal fluid can be taken through a lumbar puncture (spinal tap).
  • A biopsy sample may be taken using a needle or other tool.

How It Feels

The amount of discomfort or pain you feel depends on the method used to collect a sample for the test. Generally, a viral test does not cause pain or the pain goes away after the test.


Generally, the chance of problems from the test depends on the method used to collect a sample for testing. Your doctor can talk to you about any specific risks of the test.


A viral test is done to find infection-causing viruses.

It may take as little as 1 day or up to several weeks to get test results.

The results of some viral tests (antibody or antigen tests) are reported in titers. A titer is a measure of how much the sample can be diluted before the viral antibodies or antigens can no longer be detected.

WebMD Medical Reference from Healthwise

Last Updated: September 09, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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