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 | Rare | Common and high (102 - 104 F); lasts 3 - 4 days |
Headache | Rare | 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. However, such tests can be very helpful in confirming or ruling out the flu. 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.
A nasopharyngeal culture is a test used to identify disease-causing organisms in nasal secretions. Nasopharyngeal cultures are useful in identifying Bordetella pertussis and Neisseria meningitidis (types of bacteria). The culture may help determine appropriate antibiotic therapy.
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 new, 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.
Other Causes of Congestion
Ruling out Allergic Rhinitis. Symptoms of allergic rhinitis include nasal obstruction and congestion, which are similar to the symptoms of a cold. People with allergies, however, are likely to have the following:
- Thin, clear, and runny nasal discharge
- An itchy nose, eyes, or throat
- Recurrent sneezing
There are two forms of allergic rhinitis:
