How is avian influenza detected in humans?

Medicine Net explained that:

Avian influenza cannot be diagnosed by symptoms alone, so a laboratory test is required. Avian influenza is usually diagnosed by collecting a swab from the nose or throat during the first few days of illness. This swab is then sent to a laboratory, where they will either look for avian influenza virus using a molecular test, or they will try to grow the virus. Growing avian influenza viruses should only be done in laboratories with high levels of protection. If it is late in the illness, it may be difficult to find an avian influenza virus directly using these methods. If this is the case, it may still be possible to diagnose avian influenza by looking for evidence of the body’s response to the virus. This is not always an option because it requires two blood specimens (one taken during the first few days of illness and another taken some weeks later), and it can take several weeks to verify the results.