Bird Flu (cont.)
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Bird Flu Diagnosis
There is no way to tell what type of influenza a person has without doing tests. In most cases, the diagnosis of flu is determined by the symptoms, especially when these occur during the peak flu season (late fall and winter in the U.S.). Sometimes, the doctor may need to perform special tests to be sure the seasonal influenza virus is responsible for the symptoms.
To identify whether the virus is present and to test for the type of influenza, a sample is taken from the back of the throat and/or nose. The doctor uses a cotton-tipped wooden stick and simply rubs the cotton tip at the back of the throat and/or inside the nose. Alternatively, samples may be obtained by rinsing saltwater (saline) solution through the nose and throat and aspirating the fluid back into a specimen jar. The sample is sealed in a packet and sent to the lab for testing. Some offices may use a rapid test that can be done in the office with the result available in 30 minutes. Some rapid tests detect only influenza A virus, while others can detect both influenza A and influenza B virus types. Some cases of flu may be missed by the rapid tests. There are no commercially available tests that specifically detect bird flu. However, Chinese researchers are attempting to quickly develop a test to identify H7N9 viral infections.
Again, routine diagnostic tests available in the doctor's office currently cannot determine whether a case of the flu is due to bird flu or human flu. The patient's samples would be sent to a reference laboratory (usually through the health department) for special testing if bird flu is suspected (perhaps because of a known exposure to infected birds). If a patient is in the hospital, the physician may recommend a bronchoscopy, which involves slipping a tube through the mouth into the lungs to aspirate secretions. Most viruses can be identified fairly quickly by polymerase chain reaction (PCR), usually done at the CDC. However, the CDC, like the Chinese research community, is attempting to develop similar tests for H7N9. The virus may also be cultivated in tissue culture and antibodies against it may also be detected in an infected person's serum, but these tests take time. The patient usually has either recovered or died by the time these tests are done.
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