Table of Contents
Diagnosis
Differentiating between a cold and flu may be difficult. Cold symptoms are nearly always less severe than those of the flu.
Comparing Colds and Flus | ||
| Symptoms | Cold | Flu |
Fever |
None or low grade |
Common and high (102 - 104 °F); lasts 3 - 4 days |
Headache |
None or mild |
Almost always present |
General aches and pains |
Mild, if they occur at all |
Often severe |
Fatigue, exhaustion, and weakness |
Mild, it they occur at all |
Extreme exhaustion is early and severe; can last 2 - 3 weeks |
Stuffy nose |
Nearly always |
Sometimes |
Sneezing |
Very common |
Sometimes |
Sore throat |
Common |
Sometimes |
Chest discomfort and cough |
Mild-to-moderate, hacking cough |
Common, can be severe |
Source: National Institute of Allergy and Infectious Disease | ||
Diagnosing the Flu
Several available tests can isolate and identify the viruses responsible for some respiratory infections. They are generally not needed, since most cases of the flu are self-evident. Decisions about treatment are almost always made based on how sick an individual is, and whether the person is at risk for more severe complications. If a doctor believes a diagnosis would help, samples using a swab should be taken from the nasal passages or throat within 4 days of the first symptoms.
Several rapid tests for the flu can produce results in less than 30 minutes, but vary on the specific strain or strains that they can detect. They are not as accurate as a viral culture, however, in which the virus is reproduced in the laboratory. Culture results can take 3 - 10 days. Blood tests can also document the infection several weeks after symptoms appear.
Diagnosing Avian Influenza
In February 2006, the U.S. Food and Drug Administration approved a faster test for diagnosing H5 strains of avian influenza in people suspected of having the virus. The test is called the Influenza A/H5 (Asian lineage) Virus Real-time RT-PCR Primer and Probe Set. The test gives preliminary results within 4 hours. Older tests required 2 - 3 days. It checks for the presence of the Influenza A H5 strain. If the presence of this strain is confirmed through the rapid test, further testing will be needed to determine the exact subtype of the virus. For example, the current strain of concern is H5, subtype N1, designated as H5N1 for short.
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Review Date: 01/29/2011
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine,
Harvard Medical School; Physician, Massachusetts General Hospital.
Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M.,
Inc.
A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)
