The FDA has issued warning letters to nine companies marketing bogus flu products which claim that they could be effective against preventing the avian flu or other forms of influenza. The agency is not aware of any scientific evidence that demonstrates the safety or effectiveness of these products for treating or preventing avian flu and is concerned that the use of these products could harm consumers or interfere with conventional treatments. Examples of the unproven claims include "prevents avian flu," "a natural virus shield," "kills the virus," and "treats the avian flu." The companies have 15 days to respond. Consumers who believe that they have seen a fraudulent product can report it to the FDA at http://www.fda.gov/oc/buyonline/buyonlineform.htm.