The Health Department officials said the death of a 53-year-old woman on Wednesday night could be because of dengue.
Mangalore Taluk Health Officer Ratnakar said Julian, wife of a Karnataka State Reserve Police official, had gone to Karwar a few days ago.
She returned to Mangalore on Tuesday with fever and was admitted in the Father Muller Hospital.
The initial test (NS 1) showed her positive for dengue. However, the Elisa confirmatory test showed negative for dengue.
Dr. Ratnakar said the hospital found her platelets dropping to 27,000. She died following internal bleeding.
Dr. Ratnakar said following the decrease in platelet count pointed to a case of dengue.
Precautionary measures including measures to clear mosquito breeding sites in Assaigoli has been taken, he said.