Novel influenza A virus reagents are used to directly detect and differentiate novel influenza A virus specific nonstructural protein 1 (NS1) in human respiratory specimens or viral cultures. Detection and differentiation of specific NS1 protein aids in the diagnosis of influenza caused by novel influenza A viruses in patients with clinical and epidemiological risk of infection with these viruses. They also aid in the presumptive identification of specific novel influenza A viruses and provide epidemiological information on influenza.