How to check for viral infections

Dec 01, 2025 Source: Cainiu Health

Dr. Ren Yi

Introduction

Methods for detecting viral infections include nucleic acid testing, antigen testing, antibody testing, virus isolation and culture, and blood routine tests for auxiliary diagnosis. Nucleic acid testing detects specific viral nucleic acid fragments in samples using specialized techniques, offering high sensitivity and specificity. Commonly used samples include nasopharyngeal swabs, oropharyngeal swabs, blood, and sputum, which can directly confirm the presence of the virus in the body.

Generally, methods for detecting viral infections include nucleic acid testing, antigen testing, antibody testing, virus isolation and culture, and routine blood tests for auxiliary diagnosis. Specific analyses are as follows:

1. Nucleic Acid Testing: This method detects specific viral nucleic acid fragments in samples using specialized techniques, offering high sensitivity and specificity. Commonly used samples include nasopharyngeal swabs, oropharyngeal swabs, blood, and sputum. It can directly confirm the presence of a virus in the body and is an important tool for early diagnosis of most viral infections.

2. Antigen Testing: This detects antigenic substances on the surface of the virus in samples. It is relatively simple to perform and provides rapid results. Colloidal gold assays are commonly used, with nasopharyngeal or oropharyngeal swabs as specimens. It is suitable for rapid screening but has slightly lower sensitivity compared to nucleic acid testing, and false-negative results may occur.

3. Antibody Testing: This detects antibodies (IgM and IgG) produced by the body in response to a viral infection, using blood samples. A positive IgM result typically indicates recent infection, while a positive IgG result suggests past infection or established immunity. This test helps assess the stage of infection and immune status.

4. Virus Isolation and Culture: This involves isolating live virus from patient samples and culturing it, considered the gold standard for diagnosing viral infections. However, it is technically complex, time-consuming, and requires high-level laboratory conditions. It is mainly used in research, viral typing, or confirmation of special cases, and is rarely employed in routine clinical testing.

5. Routine Blood Test for Auxiliary Diagnosis: This evaluates indicators such as white blood cell and lymphocyte counts to assist in diagnosis. Some viral infections may cause increases or decreases in lymphocyte counts. Combined with clinical symptoms and other test results, this method can provide preliminary evidence of a viral infection, although it cannot identify the specific type of virus.

When undergoing tests for viral infection, the appropriate method should be selected based on the suspected virus type, and sample collection should follow healthcare professionals' instructions. Avoid taking antiviral medications on your own before testing, as this may affect the accuracy of results. After receiving test results, consult a doctor promptly for professional interpretation and guidance on subsequent management.

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