So far there have been no reported cases of virus transmission to humans. People with bird flu-like symptoms have been tested, but all were negative for avian flu. H5N1 is extremely contagious, and when it transmits to humans it has a high mortality rate. Che Abdullah and officials believe the virus was imported, but there is no determined cause of the outbreak yet. Veterinary officials believe the virus may have been brought in from cockfighting roosters from neighboring countries.