The recent outbreak of Zika virus (ZIKV) infection has led to a serious threat to public health. Rapid and sensitive diagnostics for ZIKV infection are crucial because Zika infection is usually mild and often asymptomatic, but may have serious consequences to infants born to infected mothers. We report on a simple, sensitive, inexpensive, point-of-care (POC) diagnostic technology for rapid detection of ZIKV in saliva. We use a chemically heated cup for isothermal amplification without a need for electrical power. The detection results can be directly read out by eye.