Nowadays, the widespread deployment of more powerful devices (sensors, smartphones, tablets, etc.) has provided us with great number sources of sensing data that are exploited in several domains namely the healthcare domain. Chronic diseases are the most common causes of death and disability worldwide. These types of diseases require more and more studies to help patients and notify cases of crises that lead to death. Representing knowledge through building an ontology for emergency alert system is important to achieve semantic interoperability among health information, predict the patient real-time context and to better execute decision notification. Linked Open Data services are used in our paper in order to provide with the semantic description of collected data from different sources (wearable sensors, environmental sensors, etc.).