There is no perfect test for the diagnosis of infl uenza. Virus culture, the present 'gold-standard test' is not 100% sensitive and does not provide results in a time-frame that allows optimal use of potentially effective antiviral treatment. Although rapid diagnostic tests provide results in less than 30 minutes, they are signifi cantly less sensitive and do not differentiate between different subtypes of infl uenza A virus. Rapid testing is only offered after the fi rst culture-confi rmed cases of infl uenza are reported from the community. Molecular assays; reverse transcriptase polymerase chain reaction (RT-PCR) and real-time RT-PCR targeting conserved regions of infl uenza virus genome have advantages over other methods and provide sensitive, highly specifi c and rapid diagnosis. The realtime RT-PCR should be the method of choice and both in-house developed and CDC-developed real-time PCR assays can be used for the specifi c detection of novel H1N1 2009 infl uenza virus. Influenza A: From highly pathogenic H5N1 to pandemic 2009 H1N1. Epidemiology and clinical features The last decade has seen the emergence of two new influenza A subtypes and they have become a cause of concern for the global community. These are the highly pathogenic H5N1 influenza A virus (H5N1) and the Pandemic 2009 influenza H1N1 virus. Since 2003 the H5N1 virus has caused widespread disease and death in poultry, mainly in south East Asia and Africa. In humans the number of cases infected with this virus is few but the mortality has been about 60%. Most patients have presented with severe pneumonia and acute respiratory distress syndrome. The second influenza virus, the pandemic H1N1 2009, emerged in Mexico in March this year. This virus acquired the ability for sustained human to human spread and within a few months spread throughout the world and infected over 4 lakh individuals. The symptoms of infection with this virus are similar to seasonal influenza but it currently affecting younger individuals more often. Fortunately the mortality has been low. Both these new influenza viruses are currently circulating and have different clinical and epidemiological characteristics. Infl uenza is an acute respiratory disease which affects the upper and/or lower respiratory tracts. Infl uenza outbreaks occur every year and globally account for about 3-5 million severe cases with 250,000 to 500,000 deaths annually. It is caused by infl uenza viruses which are of three types: A, B and C and they can all affect humans.