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Influenza Tests
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Common Questions
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1. What other tests might my doctor order to diagnose my flu-like symptoms?
2. Why is the flu such a big deal?
3. Can I still get the flu if I've had the vaccination?
1. What other tests might my doctor order to diagnose my flu-like symptoms?
Your doctor may order a strep test to check for strep throat, blood cultures to check for bacterial infections in the blood, an RSV antigen test (respiratory syncytial virus - a virus that often infects young children and the elderly), or a sputum culture to look for bacterial and/or fungal causes of a respiratory infection. They may also order blood tests such as a CMP (Comprehensive Metabolic Panel) or CBC (Complete blood count) to monitor body organ function.
2. Why is the flu such a big deal?
It is because the flu can be deadly and because every few decades an especially lethal influenza emerges. The worst on record is the 1918 Spanish flu pandemic (large scale epidemic), which killed more than 20 million people worldwide, 500,000 in the United States alone. In 1957 and 1968 hundreds of thousands died in the U.S. from Asian and Hong Kong flu variants. The new strain of influenza A, named for its unique viral antigens (H5N1), is circulating in birds and chickens in Asia. It has infected humans who have had close contact with the infected birds and has a high morality rate. There is concern of a world-wide pandemic if this virus is able to mutate to allow human-to-human transmission of the virus.
3. Can I still get the flu if I've had the vaccination?
Yes. Influenza circles around the globe and moves through communities. As it travels, it undergoes spontaneous changes (called "antigenic drift") that allow it to evade the protections of last year's flu shot and re-infect you. The amount of the antigen drift varies from year to year. Bigger drifts often result in more severe illnesses. Doctors and researchers carefully track the influenza virus as it moves through the world and try to anticipate the strain(s) that will eventually appear in the United States the next season. Each year the flu vaccine is produced based on their observations and experience, targeted to protect us against the expected strain. It contains inactivated virus to protect us against both influenza A and B.
In most cases, the flu vaccine will prevent the flu, but it requires a few weeks before it provides protection and it is not 100% effective. In addition, sometimes the flu will "breakthrough" -- there will have been enough antigenic drift during the season that the virus will appear slightly different to the body's immune system, decreasing the effectiveness of the vaccine's protection. Or, the flu that predominates may end up being an unexpected strain, not the ones that the vaccine was developed to protect against. Usually in these cases the vaccination will at least lessen the severity of the infection. In individual high risk patients (those with heart, kidney, and lung ailments for instance), doctors may bolster the protection by prescribing anti-viral treatments as prophylactics -- they can provide short term protection while influenza moves through the community (although this comes at a price in terms of cost and medication side effects).
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This article was last reviewed on
July 20, 2006.
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