Marker color reflects the noteworthiness of events at a particular location during a given time window. An event's degree of noteworthiness is based on the significance rating of the alert provided by HealthMap users. In the absence of user ratings, the system assigns a composite score based on the disease importance and the news volume associated with the alert. If a location's marker has multiple alerts, the color associated with the most prominent alert is used.
The large circle indicates a country-level alert, while state, province and local alerts are indicated by the small circle.