A flexible diagnostic platform is realized and its performance is demonstrated for early detection of avian influenza virus (AIV) subtype H1N1 DNA sequences. The key component of the platform is high-performance biosensors based on high output currents and low power dissipation Si nanowire field effect transistors (SiNW-FETs) fabricated on flexible 100 μm thick polyimide foils. The devices on a polymeric support are about ten times lighter compared to their rigid counterparts on Si wafers and can be prepared on large areas. While the latter potentially allows reducing the fabrication costs per device, the former makes them cost efficient for high-volume delivery to medical institutions in, e.g., developing countries. The flexible devices withstand bending down to a 7.5 mm radius and do not degrade in performance even after 1000 consecutive bending cycles. In addition to these remarkable mechanical properties, on the analytic side, the diagnostic platform allows fast detection of specific DNA sequences of AIV subtype H1N1 with a limit of detection of 40 × 10^-12 m within 30 min suggesting its suitability for early stage disease diagnosis. A flexible light weight diagnostic platform based on Si nanowire field effect transistors is realized revealing limit of detection at 40 pm for avian influenza virus subtype H1N1. A strong advantage of flexible biosensors is the large area fabrication and adaptivity by redesigning the final product on demand. These devices are cost-efficient for high-volume delivery to medical institutions world-wide.