Not very long back there was a fear that a pandemic would spread all over the world. Europe, parts of Africa and Asia were the worst affected. It was the fear of the deadly bird flu. The avian influenza H5N1) is not expected to disappear completely from these parts of the world very soon feels the WHO. It is likely that that H5N1 infection amongst birds and its subsequent infections in the humans resulting due to direct contact with infected poultry will continue to occur. So far, the spread of H5N1 virus from person to person has been rare and limited. Bird flu or the avian influenza virus usually refers to influenza A virus, found mainly in birds. The infection may also occur in humans. But such cases are rare. However, confirmed cases of human infection have been reported since 1997 which killed 6 of 18 victims of bird flu. Over the time, the influenza A virus (H5N1) seems to have developed the ability to infect more and more species of birds, and has found its way into mammals - specifically, cats that have eaten infected birds. In 1918, bird flu infected humans and killed at least 50 million people within a few months. Similarly in 1957, the Asian flu caused between one to four million deaths, while in 1968, the Hong Kong flu caused one to two million human deaths. Virologists agree that we are due for another pandemic but when is the big question. We just managed to miss is last year. What makes it more worrying is that, like the 1918 virus, the H5N1 virus seems to becoming more deadly to humans. Scientists are concerned that H5N1 virus one day could be able to infect humans and spread easily from one person to another. The impact of Bird Flu was largely in China last year. As the viruses do not commonly infect humans and spread easily from one to another, there is little or no immune protection against them in human population. Virologists believe that we can make vaccines for the H5N1 strain, but the question lies that do we have the time to test these vaccines first and then manufacture them. The only back up or treatment of bird flu is in the absence of any vaccine is the antiviral drug. A few new drugs are in the pipeline and there are classes of drugs used for blood pressure and cholesterol which may prove helpful in the treatment of bird flu. Drugs like amantadine and rimantadine which are used as antiviral medications seems to have developed resistance in the treatment of H5N1 virus. There are various studies going on to test the effectiveness of oseltamavir and zanamavir (relenza), another two anti viral medication commonly used in influenza. Most of the existing drugs are in short supply. Several generic manufacturers are now making Tamiflu, the main antiviral, although it is not clear whether H5N1 is resistant to it or not.