So far, the spread of the H5N1 virus from person to person has been rare and has not continued beyond one person. Nonetheless, because all influenza viruses have the ability to change, scientists are concerned that H5N1 virus could, one day, be able to infect humans and spread easily from one person to another.
Because these viruses do not commonly infect humans, there is little or no immune protection against them in the human population. If H5N1 virus were to gain the capacity to spread easily from person to person, an influenza pandemic (worldwide outbreak of disease) could begin. Although no one can predict when a pandemic might occur, experts from around the world are watching the H5N1 situation in Asia and Europe closely and are preparing for the possibility that the virus may begin to spread more easily and widely from person to person.
The H5N1 virus that has caused human illness and death in Asia is resistant to amantadine and rimantadine, two antiviral drugs commonly used for influenza treatment. Two other antiviral medications, oseltamivir and zanamivir, may work for the treatment of influenza caused by H5N1 virus, but additional studies still need to be done to demonstrate their effectiveness.
There currently is no commercially available flu vaccine to protect humans against the H5N1 virus that is being seen in Asia and Europe. However, vaccine development efforts are taking place. Research studies to test a vaccine to protect humans against H5N1 virus began in April 2005, and a series of clinical trials is under way.