Flu (Influenza)

Home » Flu (Influenza) » Diagnosis

Diagnosis

Flu symptoms are similar to those caused by other respiratory viruses. When the influenza virus is present in a local area, acute respiratory illness that also causes fever, muscle aches, malaise (feeling unwell), and extreme tiredness usually is the flu.

Secretions from the throat or nose can be used to make a definitive diagnosis of the flu. In these tests (e.g., nasal swab, nasopharyngeal swab, nasal wash), a sample of secretions from the nose and/or throat is taken using a cotton swab and is examined under a microscope for the presence of the influenza virus.

In some cases, cells from the sample are grown in a laboratory setting (called a viral culture). Results of a viral culture usually are available in about 3–10 days. A viral culture is necessary to determine the strain of the flu (i.e., subtype of the influenza A or B virus) and to identify other causes of the illness. Information about the strain of flu virus is used to develop the flu vaccine for the following year.

More recently, rapid tests have been developed that can detect the influenza virus in as little as 30 minutes to 24 hours. These tests can accurately detect the flu virus in more than 70% of cases and can identify the strain of the flu in about 90% of these cases.

Blood tests also can be used to detect recent influenza infection. A small amount of blood usually is drawn within the first week of the illness and another sample is drawn 2–4 weeks later. If the level of flu antibodies in the blood increases from one sample to the next, influenza infection is likely.

© 1998-2008 Healthcommunities.com, Inc. All Rights Reserved.

Flu (Influenza) Resources

	Join Our Cold and Flu Forum Do you have a question, want to share medical advice, or just need to discuss your situation with someone else having a similar experience? The healthchannels forum is a resource for everyone to share and discuss their health and medical needs with others.	Advertising Disclaimer
	Living with...Share your story Do you have a personal health story that you would like to share with others? As a source of free patient education, our goal is to provide our users with trustworthy information and support from others. That's why we've started our "Living with..." sections.
	Our "Living With..." support pages are a place to share experiences about living with a certain condition, disease, disorder, or illness and for loved ones of those dealing with health-related issues. Many people, especially when newly diagnosed, find comfort in knowing that others are having a similar experience. Help others by sharing your story. View stories already submitted.
	Stay Updated Sign up for our newsletter and receive important updates on the medical conditions that are most important to you.
Are you interested in becoming a nurse? Take this test. Advertising Disclaimer To quickly access health information from your website's browser, download Healthcommunities.com's healthchannels toolbar. Advertising Disclaimer