An aberration detection-based approach for sentinel syndromic surveillance of COVID-19 and other novel influenza-like illnesses

•Early detection of COVID-19 resurgence is achievable using syndromic surveillance.•Outbreaks of diseases affect in-hospital symptom prevalence distributions.•Autoencoder-based aberration detection can be used to detect outbreaks early.•Autoencoder approach can differentiate between diseases with similar syndromes.•Signals present more than one month prior to first laboratory confirmed case.