Israel’s Ministry of Health has reported a concerning outbreak of West Nile fever, with 19 patients diagnosed since the beginning of May.

According to Report, which cites the ministry, among the affected individuals, 17 have been hospitalized, and three are in critical condition, requiring artificial ventilation support.

The majority of cases have been identified in central Israel, raising alarms about the spread of the mosquito-borne disease.

Typically, West Nile fever outbreaks in Israel occur between June and November. However, this year’s early surge has health officials worried.